Biochemical screening is a study of the blood of a pregnant woman to determine specific markers that help determine the likelihood of a severe genetic disorder in the fetus.

From the moment of its formation, the placenta begins to produce certain substances, which then penetrate into the mother's blood. The number of these markers in the norm is constantly changing as the fetus develops. The determination of these substances is the basis of biochemical screening: significant deviations of the obtained results from accepted norms and talk about the high possibility of having chromosomal abnormalities or.

information Of course, such laboratory studies cannot make a diagnosis, but they help to select a group of women with a high risk of having children with pathology and offer them further in-depth examination to clarify the situation.

Biochemical screening is performed twice during the entire period of bearing a child: in the first trimester (10-14 weeks) and in the second trimester (16-20 weeks).

Indications for carrying out

The question of the need to perform biochemical screening in all pregnant women is still controversial. Most experts recommend doing this test to all patients, because no one is immune from genetic disorders. The World Health Organization (WHO) recommends at least mandatory laboratory tests in all pregnant women.

This analysis is not mandatory, and the decision to perform is voluntary for each expectant mother, although, of course, it will not hurt to insure yourself once again.

In addition, groups of women who have a high risk of having children with a genetic pathology have been identified. Such patients should be examined twice during the entire gestation period.

At-risk groups requiring mandatory biochemical screening:

• The age of a woman is over 30 years old during the first pregnancy and over 35 years old during the second and subsequent;
• 2 or more spontaneous abortions in history;
• Self-administration of drugs in the early stages that have a teratogenic effect;
• Infectious diseases suffered in the first trimester;
• The presence in the family of relatives with genetic abnormalities;
• The presence of genetic abnormalities in one or both parents;
• Birth earlier in the family of a child with genetic abnormalities;
• Stillbirth or death of another child from malformations in the family earlier;
• Marriage between close relatives;
• Radiation exposure of one or both parents before conception or in early pregnancy;
• Abnormalities found on fetal ultrasound.

First biochemical screening

Biochemical screening of the 1st trimester is performed at 10-14 weeks, but most experts consider it more informative to conduct a study at 11-13 weeks.

The first screening is a "double test" i.e. two substances are determined in the blood: (in particular, a free unit of human chorionic gonadotropin) and PAPP-A (plasma protein A associated with pregnancy).

Norms

Chorionic gonadotropin is secreted by the cells of the chorion (the shell of the embryo), so it begins to be determined in the blood quite early (already in the first days after the conception has occurred). Further, its amount gradually increases, reaches a maximum by the end of the first trimester, then begins to decline and remains at a constant level from the second half of pregnancy.

Normal levels of hCG

RAPP-A- This is a protein produced by the trophoblast throughout the entire gestation period, its amount increases constantly in proportion to the gestational age.

Normal indicators of PAPP-A

additionally The result of biochemical screening is evaluated not only by the results obtained, but also by the value of MoM, which ultimately is the determining factor. MoM is a coefficient showing the degree of deviation of the obtained indicator from the average statistical normal indicator for a given gestational age. The MoM norm is from 0.5 to 2.5 (with multiple pregnancy up to 3.5 MoM).

Decryption

Deciphering biochemical screeningshould only be carried out by a physician. It should be borne in mind that each laboratory, depending on the reagents used, may have its own performance standards, in connection with this, using incorrect data, you can get false results.

Deciphering the analysis for hCG

Deciphering the analysis for PAPP-A

Biochemical screening in the second trimester

Biochemical screening of the 2nd trimester consists of a "triple test": determination of AFP (alpha-fetoprotein), hCG and free estriol. The analysis is performed from 16 to 20 weeks, but the most informative examination will be at 16-18 weeks.

Norms of the "triple test"

AFP- a protein produced in the gastrointestinal tract and liver of the fetus from the early stages of its development.

Normal AFP levels

Normal levels of hCG

Free estriol- This is a hormone produced initially only by the placenta, and then by the liver of the child. During the normal course of pregnancy, the amount of free estriol constantly increases.

Normal levels of free estriol during pregnancy

Decryption

2 biochemical screening should also be deciphered only by the attending physician, taking into account the standards of this laboratory.

Deciphering the analysis for AFP

Deciphering the analysis for free estriol

At present, a screening system is being introduced into medical practice quite successfully - a short but rather informative examination. It usually includes a small list of diagnostic procedures, after which one can suspect or refute a person's pathology. Moreover, such studies immediately form groups of people where measures are required for additional diagnostic search.

Most widely, this method has proven itself in obstetrics - there now exists a whole system called prenatal screening (that is, carried out before the birth of a child). In this case, the initial examination is performed in the first trimester of pregnancy - in a period of about 12 weeks. An ultrasound examination of the fetus at this time provides little information, revealing only gross malformations. Therefore, biochemical tests with good sensitivity come to the rescue.

Now, for diagnosis in the mother's blood, two indicators are determined - PAPP-A and hCG (human chorionic gonadotropin). The first of them also has a rather complicated name - pregnancy-associated plasma protein A. Their level directly depends on the proper development of the fetal membranes, as well as the normal formation of the embryo itself. Therefore, a change in these indicators above or below the norm may be a sign of a serious pathology.

Early prenatal screening

Under this concept, women usually represent only an ultrasound examination, which is remembered due to the imaging effect. The fact that blood was taken from a vein seems to be an insignificant event. Namely, a biochemical analysis in a period of about 12 weeks provides basic information about the normal course of pregnancy. Modern early screening is complex and includes three components:

1. Ultrasound only “superficially” concerns the examination of the embryo itself - only the coccygeal-parietal size is evaluated, as well as the ratio of the head and body. More attention is paid to its location in the uterine cavity - it is important to exclude a frozen or regressing pregnancy, or its ectopic nature.
2. The hCG assessment already reveals the normal processes of growth and development from the inside. Chorionic gonadotropin has a hormone-like effect, ensuring the proper formation of the membranes and placenta. Therefore, a change in its level is characteristic of many pathological conditions and diseases that affect the mother's or child's body.
3. The analysis of PAPP-A already has a more specific character - normally, the content of this biologically active substance in the blood in a period of 12 weeks is within the normal range. If its decrease is noted, then the probability of chromosomal abnormalities in the fetus (most often Down syndrome) is high.

Evaluation of the results of prenatal screening is carried out only by a doctor, who, on their basis, makes a decision on the need for additional diagnostics.

RAPP-A

The determination of the level of this substance in the blood began to be carried out relatively recently - the test itself has become an excellent addition to the analysis for hCG. This was due to the high sensitivity of the latter method - too many diseases and conditions cause a change in its indicators. Therefore, a simple and quick study was developed, albeit with a strange and complicated name:

• The method is based on determining the level of pregnancy-associated plasma protein A in the blood. In a woman's body, this substance is responsible for regulating the work of insulin-like growth factors, which affects the growth processes in the body.


• As a result of the research, a connection was proved between a decrease in the level of PAPP-A in pregnant women and chromosomal abnormalities in the fetus. Moreover, the greatest sensitivity and specificity was noted in the case of a change in the number of chromosomes. Therefore, the test began to be used primarily for the early detection of Down syndrome.
• But the indicators have diagnostic value only in the first trimester - in the period from 8 to 13 weeks. Therefore, this biochemical analysis needs to be combined with early prenatal screening.
• Carrying out the technique in the second trimester no longer gives informative and accurate results.

The standard unit of measurement for this assay is mU/mL, although the modern integral index (MoM) is more commonly used in evaluating results.

Grade

A quantitative change in the level of PAPP-A is only in a certain case a cause for serious concern. Moreover, a pronounced decrease in the indicator, combined with increased hCG numbers, has a diagnostic value:

• PAPP-A during pregnancy normally reaches its maximum values ​​precisely by the 12th week. At this time, its content in venous blood can range from 0.7 to 6 mU/ml. Moreover, a large spread of values ​​\u200b\u200bis noteworthy - for this, the simultaneous assessment of the test for the level of hCG is important.


• An increase in the level of protein A is rather non-specific, and is often observed during ongoing regeneration processes. Therefore, increased analysis numbers can occur after a variety of soft tissue injuries.
• With reduced rates, it is recommended to interpret them using MoM - a special coefficient. It allows you to calculate the relative value of PAPP-A, taking into account a variety of risk factors. If a deviation is noted there, then the woman needs an additional examination.

Installed low level protein is an indication for invasive diagnostics - taking a fragment of the fetal membranes for analysis, amniotic fluid or cord blood.

hCG

Chorionic gonadotropin is quite sensitive, but almost non-specific indicator. This means that a change in its level is observed in a number of diseases, not allowing one to accurately indicate one of them. Therefore, its normal level accurately indicates only one thing - the physiological course of pregnancy:

1. This biologically active substance begins to be released into the blood soon after the fertilization of the egg. Already after about 6 days it is possible to determine its trace amounts using specific analyses.


2. The substance has an effect similar to sex hormones, further stimulating the growth of fetal membranes. Therefore, an increase in its amount is normally observed throughout the first trimester of pregnancy, when the most intensive processes of growth and development of the fetus occur.
3. The level of hCG gradually increases up to 12 weeks, after which it freezes for a while within certain limits. Then there is a gradual decrease to the minimum values ​​by the time of birth of the child.
4. Pregnancy tests are based on the biochemical reaction of the strips to human chorionic gonadotropin excreted in the urine. Such an analysis can be called qualitative - its result does not give exact figures.
5. More informative is the assessment of the level of hCG in the blood serum, which allows you to correlate the obtained values ​​\u200b\u200bwith temporary norms that change depending on the duration of pregnancy.

The wide range of fluctuations in this analysis also implies the use of an integral rating scale (MoM), which allows you to find out the influence of risk factors on the result.

Grade

The absolute values ​​of the analysis, as in the study on PAPP-A, are measured using a quantitative indicator - in mU / ml. But the biologically active substance is determined throughout pregnancy, which requires standard values ​​for almost every week:

• Normally, the level of hCG in the blood by week 12 already slightly decreases, being in the range from 6000 to 103000 mU / ml. It is noteworthy that a little earlier these figures can be three times higher, without being a sign of pathology.


• An isolated increase (without connection with PAPP-A) may be associated with an incorrect assessment of the gestational age, multiple pregnancies, endocrine disorders in the mother. Also, a similar picture is often observed when using synthetic progestogens (Dufaston).
• A complex increase in hCG and protein A almost always indicates a chromosomal abnormality in the fetus. Most often, screening allows you to suspect Down syndrome, Edwards or Patau, confirmed by an in-depth examination.
• A decrease in the level of hCG is a sign of a pathology that makes further gestation impossible or risky. The cause may be an ectopic attachment of the embryo, a frozen or non-developing pregnancy, as well as the threat of spontaneous abortion.

Chorionic gonadotropin is also evaluated in late prenatal screening, where a decrease in its values ​​indicates a delay in the growth and development of the fetus.

The concept of MoM

Since all people are quite different, and laboratory norms are of a standard nature, there is a high error in assessing biochemical parameters. To simplify the interpretation of analyzes for PAPP-A and hCG in each woman, a scale of average values ​​was created. Its work is based on the following principles:

1. Initially, absolute indicators of these biological substances are required - in mU / ml. They can both fall within the limits of normal values ​​for analyzes, and be above or below them.
2. Particular attention is paid to the borderline figures, which, upon further assessment, may go beyond the limits of the norm.
3. The calculation of the primary MoM is carried out - an indicator obtained on the basis of the ratio of the result of the analysis in a woman to the average indicator for a specific gestational age.
4. Then the woman undergoes a special questionnaire (often on a computer), which identifies or excludes the main risk factors. The main indicators are age, race, body weight, bad habits, IVF, comorbidities and aggravated pregnancy.
5. Taking into account the risks, the final MoM is derived, which can also shift above or below normal fluctuations. In the absence of pathology, the indicator is usually in the range from 0.5 to 2.5.

Such an evaluation of the results allows an individual approach to the examination of each patient, making it possible to suspect a particular disease already at the screening stage. This simplifies the further diagnostic search for the disease, allowing you to choose the most appropriate methods for its detection.

Prenatal screening examination of the first trimester consists of two procedures: ultrasound diagnostics and a blood test for the possibility of genetic pathologies of the fetus. There is nothing wrong with these events. The data obtained through the ultrasound procedure and blood tests are compared with the norm for this period, which allows you to confirm the good or bad condition of the fetus and determine the quality of the gestation process.

For the expectant mother, the main task is to maintain a good psycho-emotional and physical condition. It is also important to follow the instructions of the obstetrician-gynecologist leading the pregnancy.

Ultrasound is only one examination of the screening complex. To get complete information about the health of the baby, the doctor must check the blood of the future woman in labor for hormones, evaluate the result of a general urine and blood test

Standards for ultrasound diagnostics I screening

During the first prenatal screening in the 1st trimester, the ultrasound diagnostician pays special attention to the anatomical structures of the fetus, specifies the gestation (gestation) period based on fetometric indicators, comparing with the norm. The most carefully evaluated criterion is the thickness of the collar space (TVP), since. this is one of the main diagnostically significant parameters, which makes it possible to identify genetic diseases of the fetus during the first ultrasound procedure. With chromosomal abnormalities, the collar space is usually expanded. Weekly TVP norms are shown in the table:

When conducting ultrasound screening of the first trimester, the doctor pays special attention to the structure of the facial structures of the fetal skull, the presence and parameters of the nasal bone. At 10 weeks, it is already quite clearly defined. At 12 weeks - its size in 98% of healthy fetuses is from 2 to 3 mm. The baby's maxillary bone size is evaluated and compared with the norm, because a noticeable decrease in jaw parameters in relation to the norm indicates trisomy.

On ultrasound 1 screening, the fetal heart rate (heart rate) is recorded and also compared with the norm. The indicator depends on the gestational age. Weekly heart rate rates are shown in the table:

The main fetometric indicators at this stage during the ultrasound procedure are the coccyx-parietal (KTR) and biparietal (BPR) sizes. Their norms are given in the table:

The first screening involves an ultrasound assessment of blood flow in the venous (Arancius) duct, since in 80% of cases of its violation, a child is diagnosed with Down syndrome. And only 5% of genetically normal fetuses show such changes.

Starting from the 11th week, it becomes possible to visually recognize the bladder during ultrasound. At the 12th week, during the first ultrasound screening, its volume is assessed, since an increase in the size of the bladder is another evidence of the threat of developing trisomy (Down) syndrome.

It is best to donate blood for biochemistry on the same day that ultrasound screening is performed. Although this is not a requirement. Blood sampling is carried out on an empty stomach. The analysis of biochemical parameters, which is carried out in the first trimester, is aimed at identifying the degree of threat of occurrence genetic diseases at the fetus. For this, the following hormones and proteins are determined:

• pregnancy-associated plasma protein-A (PAPP-A);
• free hCG (component beta).

These figures depend on the week of pregnancy. The range of possible values ​​is quite wide and correlates with the ethnic content of the region. In relation to the average-normal value for this region, the level of indicators fluctuates within the following limits: 0.5-2.2 MoM. When calculating the threat and deciphering the data, not just the average value is taken for analysis, all possible amendments to the anamnestic data of the expectant mother are taken into account. Such an adjusted MoM allows you to more fully determine the threat of developing a genetic pathology of the fetus.

A blood test for hormones is necessarily performed on an empty stomach and is often scheduled on the same day as the ultrasound. Due to the presence of standards for the hormonal characteristics of the blood, the doctor can compare the results of a pregnant woman's tests with the norms, identify a deficiency or excess of certain hCG hormones: an assessment of risk values

In terms of information content, free hCG (beta component) is superior to total hCG as a marker of the risk of a genetic abnormality of the fetus. The norms of beta-hCG with a favorable course of gestation are shown in the table:

This biochemical indicator is one of the most informative. This applies to both the detection of genetic pathology and the marking of the course of the gestation process and the changes taking place in the body of a pregnant woman.

Pregnancy-Associated Plasma Protein-A Guidelines

This is a specific protein that the placenta produces throughout the entire gestational period. Its growth corresponds to the period of development of pregnancy, has its own standards for each period. If there is a decrease in the level of PAPP-A in relation to the norm, this is a reason to suspect the threat of developing a chromosomal abnormality in the fetus (Down and Edwards disease). The norms of PAPP-A indicators for normal gestation are indicated in the table:

However, the level of pregnancy-associated protein loses its information content after the 14th week (as a marker for the development of Down's disease), since after this period its level in the blood of a pregnant woman carrying a fetus with a chromosomal abnormality corresponds to a normal indicator - as in the blood of a woman who has healthy pregnancy.

Description of 1st trimester screening results

To evaluate the results of I screening, each laboratory uses a specialized computer product - certified programs that are configured for each laboratory separately. They produce a basic and individual calculation of threat indicators for the birth of a baby with a chromosomal abnormality. Based on this information, it becomes clear that it is better to take all tests in one laboratory.

The most reliable prognostic data are obtained during the first prenatal screening in the first trimester in full (biochemistry and ultrasound). When deciphering the data, both indicators of biochemical analysis are considered in combination:

low values ​​of protein-A (PAPP-A) and increased beta-hCG - the threat of developing Down's disease in a child;
low levels of protein-A and low beta-hCG - the threat of Edwards disease in a baby.
There is a fairly accurate procedure to confirm a genetic abnormality. However, this is an invasive test that can be dangerous for both the mother and the baby. To clarify the need to use this technique, the data of ultrasound diagnostics are analyzed. If there are echo signs of a genetic anomaly on an ultrasound scan, an invasive diagnosis is recommended for a woman. In the absence of ultrasound data indicating the presence of chromosomal pathology, the expectant mother is recommended to repeat biochemistry (if the period has not reached 14 weeks), or wait for the indications of the 2nd screening study in the next trimester.

Chromosomal disorders of fetal development are most easily detected using a biochemical blood test. However, if the ultrasound did not confirm the fears, it is better for the woman to repeat the study after a while, or wait for the results of the second screening Risk assessment

The information received is processed by a program specially created to solve this problem, which calculates the risks and gives a fairly accurate forecast regarding the threat of developing fetal chromosomal abnormalities (low, threshold, high). It is important to remember that the resulting transcript of the results is only a forecast, and not the final verdict.

In each country, the quantitative expressions of the levels vary. We consider a high level to be less than 1:100. This ratio means that for every 100 births (with similar test results), 1 child is born with a genetic pathology. This degree of threat is considered an absolute indication for invasive diagnostics. In our country, the threshold level is the threat of the birth of a baby with malformations in the range from 1:350 to 1:100.

Threat threshold means that a child can be born sick with a risk of 1:350 to 1:100. At a threshold level of threat, a woman is sent to an appointment with a geneticist, who gives a comprehensive assessment of the data received. The doctor, having studied the parameters and anamnesis of the pregnant woman, defines her as a risk group (with a high degree or a low one). Most often, the doctor recommends waiting until the screening study of the second trimester, and then, having received a new calculation of threats, come back to the appointment to clarify the need for invasive procedures.

The information described above should not scare expectant mothers, nor should you refuse to undergo first trimester screening. Since most pregnant women have a low risk of carrying a sick baby, they do not need additional invasive diagnostics. Even if the examination showed a poor condition of the fetus, it is better to find out about it in a timely manner and take appropriate measures.

If studies have revealed a high risk of having a sick child, the doctor must honestly convey this information to parents. In some cases, an invasive study helps to clarify the situation with the health of the fetus. With unfavorable results, it is better for a woman to terminate the pregnancy early in order to be able to bear a healthy child. If unfavorable results are obtained, what should I do?

If it so happened that the analysis of the indicators of the screening examination of the first trimester revealed a high degree of threat of the birth of a child with a genetic anomaly, first of all, you need to pull yourself together, since emotions negatively affect the bearing of the fetus. Then start planning your next steps.

First of all, it is hardly worth spending the time and money to get re-screened in another lab. If the risk analysis shows a ratio of 1:100, you can not hesitate. You should immediately contact a geneticist for advice. The less time wasted, the better. With such indicators, most likely, a traumatic method of confirming the data will be prescribed. At 13 weeks, this will be an analysis of the chorionic villus biopsy. After 13 weeks, it may be recommended to perform cordo- or amniocentesis. Analysis of the chorionic villus biopsy yields the most accurate results. The waiting time for results is about 3 weeks.

If the development of fetal chromosomal abnormalities is confirmed, the woman will be recommended artificial termination of pregnancy. The decision is definitely up to her. But if a decision is made to terminate the pregnancy, then the procedure is best done at 14-16 weeks.

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The procedure, called "screening" (from English - screening - sifting), for some reason, causes anxiety in most expectant mothers, some of whom refuse the procedure only because they are afraid to hear unpleasant news about its results.

But after all, screening, especially with the use of modern computer systems and high-precision devices, is not fortune-telling on coffee grounds, but an opportunity to look into the future and find out what is the probability that a baby with an incurable disease will be born in due time.

For parents, this is an opportunity to decide in advance whether they are ready to take care of a child who will need tremendous attention and care.

Norms of the first screening during pregnancy

Screening of the first trimester, in fact, consists of two procedures already familiar to a woman: ultrasound and blood sampling for analysis.

When preparing for the procedures, it is important to follow the recommendations of the doctor and try to remain calm.

Ultrasound norms

During an ultrasound examination, the specialist examines the structure of the embryo in detail, specifies the gestational age based on indicators such as the coccygeal-parietal size of the embryo (CTE) and the biparental size of the fetal head (BDP).

And, most importantly, makes the necessary measurements, informative for assessing the condition of the fetus.

This is, first of all:

1. The thickness of the collar space (NTP) is the most important indicator in ultrasound to identify the risk of chromosomal pathologies.

Norms for TVP depending on the age of the embryo

If TVP exceeds the normal value, then this is a reason to suspect the presence of a chromosomal abnormality in the fetus.

To determine this indicator, it is important to know the exact gestational age (in weeks and days) and not be late with the examination, since it is impossible to determine TVP from the second trimester.

1. Determination of the nasal bone - it is already visualized at 10-11 weeks of gestation, and at the 12th week it should be at least 3 mm. This is true for 98% of healthy embryos.
2. Fetal heart rate (HR) - depending on the weekly gestation period, normal indicators are:

An increased heart rate in the fetus is also one of the signs of the presence of Down syndrome.

1. The spectrum of blood flow in the Arantzian (venous) duct in the fetus. The reverse flow waveform occurs in only 5% of embryos without chromosomal abnormalities.
2. The size of the maxillary bone of the fetus - its lag in size is typical for embryos with trisomy.
3. Bladder volume - at the age of 12 weeks, the bladder is determined in most healthy embryos only from the 11th week. An enlarged bladder is an additional possible sign of Down syndrome in the fetus.

Norms of a biochemical blood test

Donating blood for screening should be done on the day of the genetic ultrasound, if possible, or, if not possible, the next day.

Ideally, blood for the screening test is taken in the morning on an empty stomach, in extreme cases, no less than 4 hours after a meal.

In the first trimester, screening for the risk of developing malformations of the embryo consists of an assessment of two indicators: the free hCG β-subunit and PAPP-A.

The range of values ​​of these blood markers that are acceptable at each stage of pregnancy (by weeks) is quite wide and may vary in the loci of screening depending on the ethnic composition of the region.

However, in relation to the median of this region - the average normal value for a particular gestational age - the level of the analyzed indicators should be from 0.5 to 2 MoM.

Moreover, when calculating the risks in each individual case, it is not the pure MoM that is taken, but the calculated one, adjusted for the anamnesis of the expectant mother, the so-called. adjusted MoM.

Free hCG β-subunit

When assessing the risk of developing fetal chromosomal diseases, the analysis of free β-hCG is more informative than the level of the hCG hormone itself.

Because the reason for the change in hCG in a woman may be conditions that are not associated with bearing a baby (hormonal diseases, taking certain drugs, etc.).

Whereas the predictable change in the level of the hCG β-subunit is specific to the state of pregnancy.

With a normally developing embryo, the indicators of free β-hCG in the blood of a woman will be approximately as follows:

Determining the level of the free subunit of β-hCG in early pregnancy carries information not only about the possible pathology of fetal development, but also about other conditions of pregnancy or changes in the woman's body.

Provided that the gestational age is set correctly and, neglecting the possibility of a false result, the reasons for the discrepancy between the level of β-hCG in the woman’s blood and the gestational age may be completely different reasons that are not related to abnormalities in the development of the fetus.

RAPP-A norms

A pregnancy-specific protein is produced by the outer layer of the placenta and is observed in a woman's blood throughout pregnancy.

Its level increases according to the duration of pregnancy.

The lag of its level from the norm for a specific period of pregnancy can act as one of the signs of the risk of pathologies in the chromosome set of the fetus: Down syndrome, Edwards syndrome.

Limits of PAPP-A indicators in the blood of a patient with a normally developing pregnancy

The value of PAPP-A, as a marker of fetal chromosomal pathologies, is alarming at a lower than average value in the region (MoM below 0.5). In the first trimester, this may mean the risk of developing Down syndrome, Edwards.

It must be borne in mind that after the 14th week of pregnancy, to determine the risk of developing Down syndrome in the fetus, the level of PAPP-A is not informative, because. compared with healthy pregnancy rates even in the presence of trisomy 21.

Deciphering the results of the first screening

To evaluate the results of prenatal screening tests, certified computer programs designed specifically for this purpose and configured to work in the home laboratory are used.

Therefore, all studies must be completed at the same institution.

Only combined screening - evaluation of ultrasound data in conjunction with the analysis of biochemical blood markers - becomes the key to obtaining a highly accurate prognosis.

Indicators of a double biochemical test conducted in the first trimester of pregnancy are considered in combination with each other.

Thus, a low level of PAPP-A in combination with an increased level of β-hCG in a woman’s blood, ceteris paribus, gives serious grounds to suspect the development of Down syndrome in the fetus, and in combination with a low level of β-hCG, the risk of developing Edwards syndrome.

In this case, the data of the ultrasound protocol become decisive for making a decision on the direction of a woman for invasive diagnostics.

If the ultrasound did not reveal pathological abnormalities in the fetus, then, as a rule, the expectant mother is recommended to undergo repeated biochemical screening, if the gestational age allows, or wait until the screening of the second trimester is possible.

Adverse first screening results

The screening data is processed by a "smart" computer program, which issues its own verdict on the risk level for the development of chromosomal pathologies in the fetus: low, threshold or high.

In our country, a risk value of less than 1:100 is considered high. This means that one out of a hundred women with similar results of the first screening has a child with malformations.

And such a risk is an unequivocal indication for an invasive examination method in order to diagnose chromosomal diseases of the embryo with 99.9% certainty.

Threshold risk means that the chance of having a child with an incurable developmental disorder is between 1:350 and 1:100 cases.

In this situation, a woman needs to consult a geneticist, whose task, after an individual appointment, to clarify in a high or low risk group refers to the bearing of a fetus with malformations future mom.

As a rule, the geneticist suggests that the woman calm down, wait and undergo additional non-invasive examinations in the second trimester (second screening), after which she invites her to a second appointment to review the results of the second screening and determine the need for invasive procedures.

Fortunately, the lucky ones who have a first trimester screening show a low risk of carrying a sick child: more than 1:350, the vast majority among expectant mothers. They do not require additional examinations.

What to do with adverse results

If, according to the results of prenatal screening, a future mother has a high risk of having a child with congenital malformations, then the first task for her is to maintain peace of mind and plan her further actions.

Future parents should determine how important accurate information about the presence of pathologies in the development of the unborn child is for them, and in this regard, decide whether to continue examinations for an accurate diagnosis.

What to do if you get bad results after the first screening?

• The first screening should not be repeated in a different laboratory.

So you will only lose precious time. And even more so, you should not wait for the second screening.

• If you get poor results, you need (at a risk of 1:100 and below) you should immediately seek advice from a geneticist.

• You should not wait for a scheduled admission to the LCD and seek a referral or an appointment with a geneticist.

You need to immediately find a qualified specialist and visit a paid appointment. The fact is that a geneticist will most likely prescribe you an invasive procedure. If the period is still small (up to 13 weeks), then this will be a biopsy of the chorionic villi.

• It is better for all women with a high risk of having a child with genetic abnormalities to undergo a chorionic villus biopsy, since the rest of the procedures to identify the fetal genotype amniocentesis, cordocentesis are performed at a later date.

The results of any invasive procedure should be expected in about 3 weeks. If you do the analysis for a fee, then a little less.

• If the anomalies in the development of the fetus are confirmed, then, depending on the decision of the family, the doctor may issue a referral for termination of pregnancy.

In this case, termination of pregnancy will be carried out for a period of 14-16 weeks.

Now imagine if you do an amniocentesis at 16-17 weeks. Wait 3 more weeks for results. And at 20 weeks, you are offered to terminate the pregnancy, when the fetus is already actively moving, when there is already a full realization that a new life lives in your body.

For a period of more than 20 weeks in a good clinic, a viable baby can be born. For a period of more than 20 weeks, abortions are not performed, but artificial births are performed for medical reasons.

Such interventions break the psyche of the woman and the father of the child. It's very hard. Therefore, it is precisely for a period of 12 weeks that a difficult decision should be made - to find out the truth and have an abortion as early as possible. Or take birth special child as a given.

Reliability of screenings and the need for them

From expectant mothers in queues to the doctor in antenatal clinics, on thematic forums, and sometimes from the doctors themselves, one can hear very different opinions about the advisability of screening during pregnancy.

And indeed. Screenings are not very informative. They do not give an accurate answer to the question of whether your child has a genetic disorder. Screening gives only a probability, and also forms a risk group.

Screening results are not a diagnosis and, moreover, not a sentence.

The first screening gives parents the opportunity to make a more accurate diagnosis and terminate the pregnancy at a short term or to prepare as much as possible for the arrival of a special child.

The absence of risks for the development of abnormalities in the development of the fetus, due to chromosomal pathologies, according to screening, will allow a young mother to calmly carry out her pregnancy, being 99% sure that her baby has passed the trouble (because the probability of false positive screening results is negligible).

Disputes about the need to undergo screenings, about their moral side, apparently, will not subside soon. However, when answering the question of whether it is worth taking a medical referral for screening, future parents should mentally move forward a few months and imagine a situation that the risks have come true.

And only realizing their readiness to accept a special baby, mom and dad can confidently write a refusal or agree to examinations.

Almost every pregnant woman has heard something about screening for the first trimester of pregnancy (prenatal screening). But often even those who have already passed it do not know what exactly it is prescribed for.

And for expectant mothers who have yet to do this, this phrase in general sometimes seems frightening. And it frightens only because the woman does not know how it is done, how to interpret the results obtained later, why the doctor needs it. You will find answers to these and many other questions related to this topic in this article.

So, more than once I had to deal with the fact that a woman, having heard an incomprehensible and unfamiliar word screening, began to draw terrible pictures in her head that frightened her, making her want to refuse to carry out this procedure. Therefore, the first thing we will tell you is what the word “screening” means.

Screening (English screening - sorting) - these are various research methods that, due to their simplicity, safety and availability, can be used massively in large groups of people to identify a number of signs. Prenatal means prenatal. Thus, we can give the following definition of the concept of "prenatal screening".

Screening of the first trimester of pregnancy is a set of diagnostic studies used in pregnant women at a certain gestational age to detect gross fetal malformations, as well as the presence or absence of indirect signs of fetal pathologies or genetic abnormalities.

The allowable period for 1st trimester screening is 11 weeks - 13 weeks and 6 days (see the weekly pregnancy calculator). Screening is not carried out earlier or later, as in this case the results obtained will not be informative and reliable. The most optimal period is considered to be 11-13 obstetric weeks of pregnancy.

Who is referred for first trimester screening?

According to order No. 457 of the Ministry of Health Russian Federation 2000, prenatal screening is recommended for all women. A woman can refuse it, no one will forcibly lead her to these studies, but doing this is extremely reckless and speaks only of the woman's illiteracy and negligent attitude towards herself and, above all, towards her child.

Risk groups for whom prenatal screening should be mandatory:

• Women who are 35 years of age or older.
• The presence of a threat of termination of pregnancy in the early stages.
• Spontaneous miscarriage(s) in history.
• Frozen (s) or regressing (s) pregnancy (s) in history.
• The presence of occupational hazards.
• Previously diagnosed chromosomal abnormalities and (or) fetal malformations as a result of screening in past pregnancies, or the presence of children born with such anomalies.
• Women who have had an infectious disease in early pregnancy.
• Women who took drugs that are prohibited for pregnant women in the early stages of pregnancy.
• The presence of alcoholism, drug addiction.
• Hereditary diseases in the family of a woman or in the family of the child's father.
• A close relationship between the mother and father of a child.

Prenatal screening at 11-13 weeks of gestation consists of two research methods - ultrasound screening of the 1st trimester and biochemical screening.

Screening Ultrasound

Preparation for the study: If the ultrasound is performed transvaginally (the probe is inserted into the vagina), then no special preparation is required. If ultrasound is performed transabdominally (the sensor is in contact with the anterior abdominal wall), then the study is performed with a full bladder. To do this, it is recommended not to urinate 3-4 hours before it, or one and a half hours before the study, drink 500-600 ml of water without gas.

Necessary conditions for obtaining reliable ultrasound data. According to the norms, screening of the first trimester in the form of ultrasound is carried out:

• Not earlier than 11 obstetric weeks and not later than 13 weeks and 6 days.
• KTP (coccyx-parietal size) of the fetus is not less than 45 mm.
• The position of the child should allow the doctor to adequately take all measurements, otherwise, it is necessary to cough, move, walk for a while so that the fetus changes its position.

As a result of ultrasound, the following indicators are examined:

• KTP (coccygeal-parietal size) - measured from the parietal bone to the coccyx
• Head circumference
• BDP (biparietal size) - the distance between the parietal tubercles
• Distance from frontal bone to occipital bone
• Symmetry of the cerebral hemispheres and its structure
• TVP (collar space thickness)
• HR (heart rate) of the fetus
• The length of the humerus, femur, as well as the bones of the forearm and lower leg
• Location of the heart and stomach in the fetus
• Dimensions of the heart and great vessels
• The location of the placenta and its thickness
• Number of waters
• The number of vessels in the umbilical cord
• Condition of the internal cervical os
• Presence or absence of uterine hypertonicity

Decryption of the received data:

What pathologies can be detected as a result of ultrasound?

According to the results of ultrasound screening of the 1st trimester, we can talk about the absence or presence of the following anomalies:

• Down syndrome is a trisomy of chromosome 21, the most common genetic disease. The prevalence of detection is 1:700 cases. Thanks to prenatal screening, the birth rate of children with Down syndrome has decreased to 1:1100 cases.
• Pathologies of neural tube development (meningocele, meningomyelocele, encephalocele and others).
• Omphalocele is a pathology in which part of internal organs is located under the skin of the anterior abdominal wall in the hernial sac.
• Patau's syndrome is a trisomy of chromosome 13. The frequency of occurrence is on average 1:10,000 cases. 95% of children born with this syndrome die within a few months due to severe damage to the internal organs. On ultrasound - rapid fetal heart rate, impaired brain development, omphalocele, slowing down the development of tubular bones.
• Edwards syndrome is trisomy 18. The frequency of occurrence is 1:7000 cases. It is more common in children whose mothers are older than 35. On ultrasound, there is a decrease in the fetal heartbeat, an omphalocele, nasal bones are not visible, one umbilical artery instead of two.
• Triploidy is a genetic anomaly in which there is a triple set of chromosomes instead of a double set. Accompanied by multiple malformations in the fetus.
• Cornelia de Lange syndrome is a genetic anomaly in which the fetus has various malformations, and in the future, mental retardation. The incidence rate is 1:10,000 cases.
• Smith-Opitz syndrome is an autosomal recessive genetic disease that manifests itself as a metabolic disorder. As a result, the child has multiple pathologies, mental retardation, autism and other symptoms. The frequency of occurrence is on average 1:30,000 cases.

More about diagnosing Down syndrome

Mostly, an ultrasound examination at 11-13 weeks of gestation is performed to detect Down syndrome. The main indicator for diagnosis is:

• The thickness of the collar space (TVP). TVP is the distance between the soft tissues of the neck and the skin. An increase in the thickness of the collar space may indicate not only an increased risk of having a child with Down syndrome, but also that other genetic pathologies in the fetus are possible.
• In children with Down syndrome, most often for a period of 11-14 weeks, the nasal bone is not visualized. The contours of the face are smoothed.

Before 11 weeks of gestation, the thickness of the collar space is so small that it cannot be adequately and reliably assessed. After 14 weeks, the lymphatic system is formed in the fetus and this space can normally be filled with lymph, so the measurement is also not reliable. The frequency of occurrence of chromosomal abnormalities in the fetus, depending on the thickness of the collar space.

When deciphering the screening data of the 1st trimester, it should be remembered that the thickness of the collar space alone is not a guide to action and does not indicate a 100% probability of a child having a disease.

Therefore, the next stage of screening of the 1st trimester is carried out - taking blood to determine the level of β-hCG and PAPP-A. Based on the obtained indicators, the risk of chromosomal pathology is calculated. If the risk according to the results of these studies is high, then an amniocentesis is suggested. It's a take amniotic fluid for a more accurate diagnosis.

In particularly difficult cases, cordocentesis may be required - taking cord blood for analysis. A chorionic villus biopsy may also be used. All of these methods are invasive and carry risks for the mother and fetus. Therefore, the decision to conduct them is decided by the woman and her doctor jointly, taking into account all the risks of conducting and refusing the procedure.

Biochemical screening of the first trimester of pregnancy

This stage of the study is carried out necessarily after ultrasound. This is an important condition, because all biochemical parameters depend on the gestational age up to the day. Every day the standards change. And ultrasound allows you to determine the gestational age with the accuracy that is necessary for a proper study. At the time of blood donation, you should already have the results of an ultrasound scan with the indicated gestational age based on the KTR. Also, an ultrasound scan may reveal a frozen pregnancy, a regressing pregnancy, in which case further examination does not make sense.

Study preparation

Blood is taken on an empty stomach! It is undesirable even to drink water in the morning of this day. If the study is carried out too late, it is allowed to drink some water. It is better to take food with you and have a snack immediately after blood sampling, rather than violate this condition.

2 days before the scheduled day of the study, you should exclude from the diet all foods that are strong allergens, even if you have never had an allergy to them - these are chocolate, nuts, seafood, as well as very fatty foods and smoked meats.

Otherwise, the risk of obtaining false results is significantly increased.

Consider what deviations from the normal values ​​of β-hCG and PAPP-A may indicate.

β-hCG - human chorionic gonadotropin

This hormone is produced by the chorion (“shell” of the fetus), thanks to this hormone, it is possible to determine the presence of pregnancy in the early stages. The level of β-hCG gradually increases in the first months of pregnancy, its maximum level is observed at 11-12 weeks of pregnancy. Then the level of β-hCG gradually decreases, remaining unchanged throughout the second half of pregnancy.

PAPP-A, pregnancy-associated protein-A

This is a protein produced by the placenta in the body of a pregnant woman, is responsible for the immune response during pregnancy, and is also responsible for the normal development and functioning of the placenta.

MoM coefficient

After receiving the results, the doctor evaluates them by calculating the MoM coefficient. This coefficient shows the deviation of the level of indicators in this woman from the average normal value. Normally, the MoM-coefficient is 0.5-2.5 (with multiple pregnancy up to 3.5).

The data of the coefficient and indicators may differ in different laboratories, the level of the hormone and protein can be calculated in other units of measurement. You should not use the data in the article as norms specifically for your study. It is necessary to interpret the results together with your doctor!

Then, using the PRISCA computer program, taking into account all the indicators obtained, the woman’s age, her bad habits (smoking), the presence of diabetes and other diseases, the woman’s weight, the number of fetuses or the presence of IVF, the risk of having a child with genetic abnormalities is calculated. A high risk is a risk of less than 1:380.

Example: If the conclusion indicates a high risk of 1:280, this means that out of 280 pregnant women with the same indicators, one will have a child with a genetic pathology.

Special situations where the indicators may be different.

• IVF - β-hCG values ​​​​will be higher, and PAPP-A - below average.
• When a woman is obese, her hormone levels may increase.
• In multiple pregnancies, β-hCG is higher and the norms for such cases have not yet been precisely established.
• Maternal diabetes can cause hormone levels to rise.

general information

Some time ago, pregnant women did not even know about such a procedure as prenatal or perinatal screening. Now all expectant mothers undergo such a survey.

What is pregnancy screening, why is it done, and why are results so important? Answers to these and other questions of concern to many pregnant women about perinatal screening we have tried to give in this material.

In order to exclude any further misunderstanding of the information presented, before proceeding directly to the consideration of the above topics, it is worth defining some medical terms.

What is ultrasound screening and biochemistry of maternal serum

Prenatal screening is a special kind of such actually standard procedure as screening. This comprehensive survey consists of ultrasound diagnostics and laboratory research blood, in this particular case maternal serum biochemistry. Early detection of some genetic abnormalities- this is the main task of such an analysis during pregnancy as screening.

prenatal or perinatal means prenatal, and under the term screening in medicine, it means a series of studies of a large stratum of the population, which are carried out in order to form the so-called "risk group", prone to certain diseases.

Can be universal or selective screening.

It means that screening studies are done not only for pregnant women, but also for other categories of people, for example, children of the same age, to establish diseases characteristic of a given period of life.

With help genetic screening doctors can learn not only about problems in the development of the baby, but also respond in time to complications during pregnancy which a woman may not even be aware of.

Often, expectant mothers, having heard that they have to go through several times this procedure start to panic and worry. However, there is nothing to be afraid of, you just need to ask the gynecologist in advance why you need screening for pregnant women, when and, most importantly, how this procedure is done.

So, let's start with what is standard screening carried out three times during the entire pregnancy, i.e. in every trimester. Recall that trimester is a period of three months.

Screening for the first trimester of pregnancy

What it is 1st trimester screening? First, let's answer the common question about how many weeks it is. first trimester of pregnancy. In gynecology, there are only two ways to reliably determine the period during pregnancy - calendar and obstetric.

The first is based on the day of conception, and the second depends on menstrual cycle, preceding fertilization. That's why I trimester- this is the period that, according to the calendar method, begins with the first week from conception and ends with the fourteenth week.

According to the second method, I trimester- This is 12 obstetric weeks. Moreover, in this case, the period is counted from the beginning of the last menstruation. Recently screening not prescribed to pregnant women.

However, now many expectant mothers themselves are interested in undergoing such an examination.

In addition, the Ministry of Health strongly recommends that examinations be ordered for all expectant mothers without exception.

True, this is done voluntarily, because. no one can force a woman to undergo any kind of analysis.

It is worth noting that there are categories of women who are simply obliged, for one reason or another, to go through screening, for example:

• pregnant women from thirty-five years and beyond;
• expectant mothers with a history of a threat spontaneous miscarriage;
• women who in the first trimester suffered infectious diseases;
• pregnant women who, for health reasons, are forced to take medicines prohibited for their position in the early stages;
• women who had various previous pregnancies genetic abnormalities or anomalies in the development of the fetus;
• women who have already given birth to children with any deviations or malformations in development;
• women who have been diagnosed frozen or regressive pregnancy(cessation of fetal development);
• suffering from narcotic or alcohol addiction women;
• pregnant women in whose family or in the family of the father of the unborn child cases of hereditary genetic abnormalities.

At what time do prenatal screening 1st trimester? For the first screening during pregnancy, the period is set in the interval starting from 11 weeks to 13 obstetric weeks of pregnancy and 6 days. Earlier than the indicated period, it makes no sense to conduct this survey, since its results will be uninformative and absolutely useless.

The first ultrasound at the 12th week of pregnancy is done by a woman for a reason. Since this is the end of embryonic and starts fetal or fetal period of human development.

This means that the embryo turns into a fetus, i.e. there are obvious changes that speak of the development of a full-fledged living human organism. As we said before, screening studies- This is a set of measures that consists of ultrasound diagnostics and biochemistry of a woman's blood.

It is important to understand that the screening ultrasound in the 1st trimester during pregnancy plays the same important role as laboratory blood tests. After all, in order for geneticists to make correct conclusions based on the results of the examination, they need to study both the results of ultrasound and the biochemistry of the patient's blood.

We talked about how many weeks the first screening is carried out, now let's move on to deciphering the results of a comprehensive study. It is really important to consider in more detail the norms established by doctors for the results of the first screening during pregnancy. Of course, only a specialist in this field who has the necessary knowledge and, most importantly, experience can give a qualified assessment of the results of the analysis.

We believe that it is advisable for any pregnant woman to know at least general information about the main indicators prenatal screening and their standard values. After all, it is common for most expectant mothers to be overly suspicious about everything related to the health of their unborn child. Therefore, they will be much more comfortable if they know in advance what to expect from the study.

Deciphering the screening of the 1st trimester by ultrasound, norms and possible deviations

All women know that during pregnancy they will have to undergo more than once an ultrasound examination (hereinafter referred to as ultrasound), which helps the doctor track the intrauterine development of the unborn child. To screening ultrasound gave reliable results, you need to prepare in advance for this procedure.

We are sure that the vast majority of pregnant women know how to do this procedure. However, it is not superfluous to repeat that there are two types of research - transvaginal and transabdominal. In the first case, the sensor of the device is inserted directly into the vagina, and in the second case it is in contact with the surface of the anterior abdominal wall.

Photo of a fetus at 13 weeks pregnant

There are no special preparation rules for the transvaginal type of ultrasound.

If you are going to have a transabdominal examination, then before the procedure (approximately 4 hours before the ultrasound), you should not go to the toilet “little by little”, and it is recommended to drink up to 600 ml of plain water in half an hour.

The thing is that the examination must be carried out necessarily on a liquid-filled bladder.

In order for the doctor to get a reliable result ultrasound screening, the following conditions must be met:

• the period of the examination is from 11 to 13 obstetric weeks;
• the position of the fetus should allow the specialist to carry out the necessary manipulations, otherwise mommy will have to “influence” the baby so that he rolls over;
• coccygeal-parietal size(hereinafter KTR) should not be less than 45 mm.

What is KTP during pregnancy on ultrasound

When conducting an ultrasound, a specialist without fail examines various parameters or sizes of the fetus. This information allows you to determine how well the baby is formed and whether it is developing correctly. The norms of these indicators depend on the gestational age.

If the value of one or another parameter obtained as a result of ultrasound deviates from the norm up or down, then this is considered a signal of the presence of some pathologies. Coccyx-parietal size- This is one of the most important initial indicators of the correct intrauterine development of the fetus.

The KTP value is compared with the fetal weight and gestational age. This indicator is determined by measuring the distance from the bone of the crown of the child to his tailbone. By general rule, the higher the KTR, the longer the gestational age.

KTR norms

When this indicator slightly exceeds or, on the contrary, slightly less than the norm, then there is no reason to panic. It speaks only about the peculiarities of the development of this particular child.

If the CTE value deviates from the standards upwards, then this indicates the development of a large-sized fetus, i.e. presumably, the weight of the child at birth will exceed the average norms of 3-3.5 kg. In cases where the CTE is significantly less than the standard values, this may be a sign that:

• pregnancy does not develop as it should, in such cases, the doctor should carefully check the fetal heartbeat. If he died in the womb, then the woman needs urgent medical care ( curettage of the uterine cavity) to prevent a possible health hazard ( development of infertility) and life ( infection, bleeding);
• the body of a pregnant woman does not produce enough hormones, usually, progesterone which can lead to spontaneous miscarriage. In such cases, the doctor prescribes an additional examination to the patient and prescribes medications containing hormones ( Utrozhestan, Dufston);
• mother is sick infectious diseases, including venereal;
• the fetus has genetic abnormalities. In such situations, doctors prescribe additional studies along with biochemical blood test, which is part of the first screening assay.

It is also worth emphasizing that there are often cases when a low CTE indicates an incorrectly established gestational age. This refers to the variant of the norm. All a woman needs in such a situation is to undergo a second ultrasound examination after a while (usually after 7-10 days).

Fetal BDP (biparietal size)

What is BDP on ultrasound during pregnancy? When conducting an ultrasound examination of the fetus in the first trimester, doctors are interested in all possible characteristics future child. Since their study gives specialists maximum information about how the intrauterine development of a little man takes place and whether everything is in order with his health.

What is it fetal BD? First, let's decipher the medical abbreviation. BDP- this is biparietal size of the fetal head, i.e. distance between walls parietal bones of the skull, in a simple way, the size of the head. This indicator is considered one of the main indicators for determining the normal development of the child.

It is important to note that BDP shows not only how well and correctly the baby is developing, but also helps doctors prepare for the upcoming delivery. Since if the size of the head of the unborn child deviates from the norm upwards, then he simply will not be able to pass through the mother's birth canal. In such cases, a planned caesarean section is prescribed.

Table of BPR norms by week

When BDP deviates from established norms, this may indicate:

• about the presence in the fetus of pathologies incompatible with life, such as cerebral herniation or tumor;
• about a sufficiently large size of the unborn child, if other basic parameters of the fetus are several weeks ahead of the established development standards;
• about spasmodic development, which after some time will return to normal, provided that other basic parameters of the fetus fit into the norm;
• on fetal development hydrocephalus of the brain arising from the presence of infectious diseases in the mother.

The deviation of this indicator downward indicates that the baby's brain is developing incorrectly.

Collar space thickness (TVP)

Fetal TVP- what it is? Collar space fetus or size neck fold- this is a place (more precisely, an oblong formation) located between the neck and the upper skin membrane of the baby's body, in which there is an accumulation of fluid. A study of this value is carried out during screening of the first trimester of pregnancy, since it is at this time that it is possible to measure TVP for the first time, and then analyze it.

Starting from the 14th week of pregnancy, this formation gradually decreases in size and by the 16th week it practically disappears from visibility. For TVP, certain norms are also established, which are directly dependent on the gestational age.

For example, the norm collar space thickness at 12 weeks should not go beyond the range of 0.8 to 2.2 mm. Collar space thickness at 13 weeks should be in the range from 0.7 to 2.5 mm.

It is important to note that for this indicator, experts set the average minimum values, the deviation from which indicates a thinning of the collar space, which, like the expansion of the TVP, is considered an anomaly.

Table of fetal TVP by week

If this indicator does not correspond to the TVP norms indicated in the above table at 12 weeks and at other stages of pregnancy, then this result most likely indicates the presence of the following chromosomal abnormalities:

• trisomy 13, a disease known as patau syndrome, characterized by the presence in human cells of an additional 13th chromosome;
• trisomy on chromosome 21, known to all as down syndrome, a human genetic disease in which karyotype(i.e., the complete set of chromosomes) is represented by the 47th chromosome instead of 46;
• monosomy on the X chromosome, a genomic disease named after the scientists who discovered it Shereshevsky-Turner syndrome, it is characterized by such anomalies of physical development as short stature, as well as sexual infantilism (immaturity);
• trisomy 18 is a chromosomal disorder. For Edwards syndrome(the second name of this disease) is characterized by a plurality of malformations that are incompatible with life.

Trisomy is an option aneuploidy, i.e. changes karyotype, in which the human cell has an additional third chromosome instead of normal diploid set.

Monosomy is an option aneuploidy (chromosomal abnormality) in which there are no chromosomes in the chromosome set.

What are the standards for trisomy 13, 18, 21 established during pregnancy? It happens that in the process of cell division a failure occurs. This phenomenon is scientifically called aneuploidy. Trisomy- this is one of the varieties of aneuploidy, in which instead of a pair of chromosomes, an extra third chromosome is present in the cell.

In other words, the child inherits from his parents an additional 13, 18 or 21 chromosome, which in turn entails genetic abnormalities that prevent normal physical and mental development. Down syndrome according to statistics, this is the most common disease due to the presence of chromosome 21.

Children born with Edwards syndrome, the same as in the case of patau syndrome, usually do not live up to a year, unlike those who are not lucky enough to be born with down syndrome. Such people can live to a ripe old age. However, such a life can rather be called existence, especially in the countries of the post-Soviet space, where these people are considered outcasts and they try to avoid and not notice them.

In order to exclude such anomalies, pregnant women, especially those at risk, must undergo a mandatory screening examination. Researchers argue that the development of genetic abnormalities is directly dependent on the age of the expectant mother. How younger woman, the less likely it is that her child will have any abnormalities.

To establish trisomy in the first trimester of pregnancy, a study is being collar space of the fetus with the help of ultrasound. In the future, pregnant women periodically take a blood test, in which for geneticists the most important indicators are the level alpha-fetoprotein (AFP), inhibin-A, human chorionic gonadotropin (hCG), and estriol.

As mentioned earlier, the risk of having a genetic abnormality in a child depends primarily on the age of the mother. However, there are cases when trisomy is fixed in young women. Therefore, when screening, doctors study all possible signs of anomalies. It is believed that an experienced ultrasound specialist can identify problems during the first screening examination.

Signs of Down syndrome, as well as Edwards and Patau

Trisomy 13 is characterized by a sharp decrease in the level PAPP-A (PAPP associated with pregnancy protein (protein) A-plasma). Also a marker of this genetic disorder is low or high hCG. The same parameters play an important role in determining whether the fetus has Edwards syndrome.

When there is no risk of trisomy 18, normal values PAPP-A and b-hCG (free beta subunit of hCG) recorded in a biochemical blood test. If these values ​​deviate from the standards established for each specific period of pregnancy, then most likely the child will have genetic malformations.

It is important to note that in the case when, during the first screening, the specialist fixes signs indicating the risk trisomy, the woman is referred for further examination and for a consultation with geneticists. To make a final diagnosis, the expectant mother will have to undergo procedures such as:

• chorion biopsy, i.e. obtaining a sample of chorion tissue for the diagnosis of anomalies;
• amniocentesis is puncture of the amniotic membrane to get a sample amniotic fluid for the purpose of their further study in the laboratory;
• placentocentesis (biopsy of the placenta), given invasive diagnostic method specialists take a sample placental tissue using a special puncture needle, which pierces anterior abdominal wall;
• cordocentesis, a method for diagnosing genetic abnormalities during pregnancy, in which the umbilical cord blood of the fetus is analyzed.

Unfortunately, if a pregnant woman has undergone any of the above studies and is bioscreening and ultrasound the diagnosis of the presence of genetic abnormalities in the fetus has been confirmed, the doctors will offer to terminate the pregnancy. In addition, unlike standard screening studies, data invasive examination methods can provoke a number of serious complications up to spontaneous miscarriage, so doctors resort to them in a fairly rare number of cases.

Nasal bone at 12 weeks, table of norms

nasal bone- This is a slightly elongated, quadrangular, convex front paired bone of the human face. At the first ultrasound screening, the specialist determines the length of the baby's nose bone. It is believed that in the presence of genetic abnormalities, this bone develops incorrectly, i.e. its ossification occurs later.

Therefore, if the nasal bone is missing or too small at the first screening, this indicates the possible presence of various anomalies. It is important to emphasize that the length of the nose bone is measured at 13 weeks or at 12 weeks. When screening at 11 weeks, the specialist checks only for its presence.

It is worth emphasizing that if the size of the nasal bone does not correspond to the established norms, but if other basic indicators are consistent, there is really no reason for concern. This state of affairs may be due to the individual characteristics of the development of this particular child.

Heart rate (HR)

A setting such as heart rate plays an important role not only in the early stages, but throughout pregnancy. Constantly measure and monitor fetal heart rate it is necessary only in order to notice deviations in time and, if necessary, save the life of the baby.

Interestingly, although myocardium (heart muscle) begins to decline as early as the third week after conception, you can hear the heartbeat only from the sixth obstetric week. It is believed that at the initial stage of fetal development, the rhythm of its heartbeats should correspond to the mother's pulse (on average, it is 83 beats per minute).

However, already in the first month intrauterine life the number of heartbeats of the baby will gradually increase (by about 3 beats per minute every day) and by the ninth week of pregnancy it will reach 175 beats per minute. Determine the fetal heart rate using ultrasound.

During the first ultrasound, specialists pay attention not only to the heart rate, but also to see how the baby's heart develops. To do this, use the so-called four-chamber cut, i.e. method of instrumental diagnosis of malformations of the heart.

It is important to emphasize that the deviation from the standards of such an indicator as heart rate indicates the presence malformations in the development of the heart. Therefore, doctors carefully study the structure on the cut atrial and fetal cardiac ventricles. If any abnormalities are found, the specialists refer the pregnant woman for additional studies, for example, echocardiography (ECG) with dopplerography.

Starting from the twentieth week, the gynecologist of the antenatal clinic will listen to the baby's heart with the power of a special tube at each scheduled visit to the pregnant woman. Such a procedure as auscultation of the heart not applied at earlier dates due to its inefficiency, tk. The doctor just can't hear the heartbeat.

However, as the baby develops, his heart will be heard more and more clearly each time. Auscultation helps the gynecologist determine the position of the fetus in the womb. For example, if the heart is better heard at the level of the mother's navel, then the child is in a transverse position, if the navel is to the left or lower, then the fetus is in cephalic presentation, and if above the navel, then in pelvic.

From the 32nd week of pregnancy, to control the heartbeat, use cardiotocography(abbreviated KTR). When conducting the above types of examinations, a specialist can record in the fetus:

• bradycardia, i.e. abnormally low heart rate which is usually temporary. This deviation may be a symptom of the mother's autoimmune diseases, anemia, preeclampsia, as well as clamping the umbilical cord, when the unborn child does not receive enough oxygen. The cause of bradycardia can be congenital heart defects in order to exclude or confirm this diagnosis, a woman is necessarily sent for additional examinations;
• tachycardia, i.e. high heart rate. Such a deviation is rarely recorded by specialists. However, if the heart rate is much higher than prescribed by the norms, then this indicates hyperthyroidism mother or hypoxia, development intrauterine infections, anemia and genetic abnormalities at the fetus. In addition, medications a woman takes can affect heart rate.

In addition to the characteristics discussed above, when conducting the first screening ultrasound, specialists also analyze the data:

• about symmetry cerebral hemispheres fetus;
• about the size of the circumference of his head;
• about the distance from the occipital to the frontal bone;
• about the length of the bones of the shoulders, hips and forearms;
• about the structure of the heart;
• about the location and thickness of the chorion (placenta or "baby place");
• about the amount of water (amniotic fluid);
• about the state of the pharynx cervix mothers;
• about the number of vessels in the umbilical cord;
• about the absence or presence uterine hypertonicity.

As a result of ultrasound, in addition to the genetic abnormalities already discussed above ( monosomy or Shereshevsky-Turner syndrome, trisomy on chromosomes 13, 18 and 21, namely Down, Patau and Edwards syndromes) the following pathologies in development can be detected:

• neural tube, for example, spinal malformation (meningomyelocele and meningocele) or craniocerebral hernia (encephalocele);
• Cornet de Lange syndrome, an anomaly in which multiple malformations are fixed, entailing both physical abnormalities and mental retardation;
• triploidy, a genetic malformation in which a failure occurs in the chromosome set, as a rule, the fetus does not survive in the presence of such a pathology;
• omphalocele, embryonic or umbilical hernia, pathology of the anterior abdominal wall, in which some organs (liver, intestines, and others) develop in a hernial sac outside the abdominal cavity;
• Smith-Opitz syndrome, a genetic disorder that affects the processes metabolism, which subsequently leads to the development of many severe pathologies, for example, autism or mental retardation.

Biochemical screening of the 1st trimester

Let's talk in more detail about the second stage of a comprehensive screening examination of pregnant women. What it is biochemical screening of the 1st trimester, And what are the standards set for its main indicators? In fact, biochemical screening- is nothing but biochemical analysis blood of the expectant mother.

This study is carried out only after ultrasound. This is due to the fact that, thanks to an ultrasound examination, the doctor determines the exact gestational age, on which the standard values ​​​​of the main indicators of blood biochemistry directly depend. So, remember that you need to go for biochemical screening only with the results of an ultrasound scan.

How to prepare for your first pregnancy screening

We talked about how they do it, and most importantly, when they do a screening ultrasound, now you should pay attention to preparing for the biochemical analysis. As in the case of any other blood test, this study must be prepared in advance.

If you want to get a reliable result of biochemical screening, you will have to follow the following recommendations exactly:

• blood for biochemical screening is taken strictly on an empty stomach, doctors do not even recommend drinking plain water, not to mention any food;
• a few days before the screening, you should change your usual diet and begin to follow a sparing diet, in which you can not eat too fatty and spicy foods (so as not to increase the level cholesterol), as well as seafood, nuts, chocolate, citrus fruits, and other food allergens, even if you have not previously had an allergic reaction to anything.

Strict adherence to these recommendations will provide a reliable result of biochemical screening. Believe me, it’s better to be patient for a while and give up your favorite treats so that you don’t worry about the results of the analysis later. After all, any deviation from the established norms, doctors will interpret as a pathology in the development of the baby.

Quite often, in various pregnancy and childbirth forums, women talk about how the results of the first screening, expected with such excitement, turned out to be bad, and they were forced to do all the procedures again. Fortunately, in the end, the pregnant women received good news about the health of their babies, since the adjusted results showed the absence of any developmental abnormalities.

The whole point was that expectant mothers were not properly prepared for screening, which ultimately led to inaccurate data.

Imagine how many nerves were spent and bitter tears were shed while women were waiting for new test results.

Such colossal stress does not pass without a trace for the health of any person, and even more so for a pregnant woman.

Biochemical screening of the 1st trimester, interpretation of the results

When conducting the first biochemical screening analysis, indicators such as free β-subunit of human chorionic gonadotropin(Further hCG), as well as PAPP-A (plasma protein A associated with pregnancy). Let's consider each of them in detail.

PAPP-A - what is it?

As mentioned above, PAPP-A- This is an indicator of a biochemical blood test of a pregnant woman, which helps specialists to establish at an early stage the presence of genetic pathologies in the development of the fetus. The full name of this quantity sounds like pregnancy-associated plasma protein A, which in literal translation into Russian means - pregnancy-associated plasma protein A.

It is protein (protein) A, produced during pregnancy by the placenta, that is responsible for the harmonious development of the unborn child. Therefore, an indicator such as the level of PAPP-A, calculated at 12 or 13 weeks during pregnancy, is considered a characteristic marker for determining genetic abnormalities.

It is mandatory to undergo an analysis to check the level of PAPP-A should:

• pregnant women over the age of 35;
• women who have previously given birth to children with genetic abnormalities;
• expectant mothers in whose family there are relatives with genetic abnormalities in development;
• women who have had diseases such as cytomegalovirus, rubella, herpes or hepatitis shortly before pregnancy;
• pregnant women who have had complications or spontaneous miscarriages in the past.

Normative values ​​of such an indicator as PAPP-A depend on the gestational age. For example, the PAPP-A rate at 12 weeks is 0.79 to 4.76 mU/mL, and at 13 weeks is 1.03 to 6.01 mU/mL. In cases where, as a result of the test, this indicator deviates from the norm, the doctor prescribes additional studies.

If the analysis revealed a low level of PAPP-A, then this may indicate the presence chromosomal abnormalities in child development, for example, down syndrome, it also signals the risk of spontaneous miscarriage and regressive pregnancy. When this indicator is increased, this is most likely the result of the fact that the doctor could not calculate the correct gestational age.

That is why blood biochemistry is taken only after an ultrasound scan. However, high PAPP-A may also indicate the likelihood of developing genetic abnormalities in the development of the fetus. Therefore, in case of any deviation from the norm, the doctor will refer the woman for an additional examination.

Scientists gave this name to this hormone not by chance, because it is thanks to him that you can reliably find out about pregnancy already 6-8 days after fertilization has occurred. eggs. It is noteworthy that hCG starts to develop chorion already in the first hours of pregnancy.

Moreover, its level is growing rapidly and by the 11-12th week of pregnancy it exceeds the initial values ​​​​by thousands of times. Then human chorionic gonadotropin gradually loses its position, and its indicators remain unchanged (starting from the second trimester) until childbirth. All pregnancy test strips contain hCG.

If the level human chorionic gonadotropin increased, this may indicate:

• about the presence of the fetus down syndrome;
• about multiple pregnancy;
• on maternal development diabetes;
• about toxicosis.

When the level of hCG is below the stipulated standards, it says:

• about a possible Edwards syndrome in the fetus;
• about risk miscarriage;
• about placental insufficiency.

After the pregnant woman has undergone ultrasound and blood biochemistry, the specialist must decipher the results of the examination, as well as calculate possible risks development of genetic anomalies or other pathologies using a special computer program PRISCA (Prisca).

The screening summary form will contain the following information:

• about age risk anomalies in development(depending on the age of the pregnant woman, possible deviations change);
• about the values ​​of biochemical parameters of a woman's blood test;
• about the risk of possible diseases;
• MoM coefficient.

In order to calculate as reliably as possible the possible risks of developing certain abnormalities in the fetus, experts calculate the so-called MoM (multiple of median) coefficient. To do this, all the obtained screening data is entered into a program that plots the deviation of each indicator of the analysis of a particular woman from the average norm established for most pregnant women.

MoM is considered normal if it does not go beyond the range of values ​​​​from 0.5 to 2.5. At the second stage, this coefficient is adjusted taking into account age, race, presence of diseases (for example, diabetes), bad habits (for example, smoking), the number of previous pregnancies, ECO and other important factors.

On the final stage the specialist makes a final conclusion. Remember, only a doctor can correctly interpret screening results. In the video below, the doctor explains all the key points related to the first screening.

1st trimester screening price

The question of how much this study costs and where it is better to take it is of concern to many women. The thing is that not every state clinic can do such a specific examination for free. Based on the reviews left on the forums, many expectant mothers do not trust free medicine at all.

Therefore, you can often meet the question of where to do screening in Moscow or other cities. If we talk about private institutions, then in a fairly well-known and well-established INVITRO laboratory, biochemical screening can be done for 1600 rubles.

True, this cost does not include ultrasound, which the specialist will definitely ask to present before conducting a biochemical analysis. Therefore, you will have to separately undergo an ultrasound examination in another place, and then go to the laboratory for blood donation. And it must be done on the same day.

Second screening during pregnancy, when to do and what is included in the study

According to the recommendations of the World Health Organization (hereinafter referred to as WHO), every woman is required to undergo three screenings throughout the entire period of pregnancy. Although in our time, gynecologists refer all pregnant women to this examination, there are those who, for whatever reason, skip screening.

However, for some categories of women, such a study should be mandatory. This applies primarily to those who have previously given birth to children with genetic abnormalities or malformations. In addition, it is mandatory to undergo screening:

• women over the age of 35, since the risk of developing various pathologies in the fetus depends on the age of the mother;
• women who in the first trimester took drugs or other illegal drugs for pregnant women;
• women who have previously suffered two or more miscarriages;
• women who suffer from one of the following diseases that are inherited to the child - diabetes mellitus, diseases of the musculoskeletal system and the cardiovascular system, as well as oncopathology;
• women who are at risk of spontaneous miscarriage.

In addition, expectant mothers should definitely undergo screening if they or their spouses were exposed to radiation before conception, and also suffered immediately before or during pregnancy. bacterial and infectious diseases. As with the first screening, the second time, the expectant mother must also do an ultrasound and pass a biochemical blood test, which is often called a triple test.

Timing of the second screening during pregnancy

So, let's answer the question of how many weeks do the second screening during pregnancy. As we have already determined, the first study is carried out in the early stages of pregnancy, namely in the period from 11 to 13 weeks of the first trimester. The next screening test is carried out during the so-called "golden" period of pregnancy, i.e. in the second trimester, which starts at 14 weeks and ends at 27 weeks.

The second trimester is called golden because it is during this period of time that all the initial ailments associated with pregnancy ( nausea, weakness, drowsiness and others) recede, and a woman can fully enjoy her new state, because she feels a powerful surge of strength.

A woman should visit her gynecologist every two weeks so that he can monitor the progress of the pregnancy.

The doctor gives the expectant mother recommendations regarding her interesting situation, and also informs the woman about what examinations and for how long she should undergo. As a standard, a pregnant woman takes a urine test and a complete blood count before each visit to the gynecologist, and the second screening takes place from 16 to 20 weeks of pregnancy.

Ultrasound screening 2nd trimester - what is it?

During the second screening first, an ultrasound scan is performed to determine the exact gestational age, so that later specialists can correctly interpret the results of a biochemical blood test. On the ultrasound the doctor studies the development and size of the internal organs of the fetus: the length of the bones, the volume chest, head and abdomen, the development of the cerebellum, lungs, brain, spine, heart, bladder, intestines, stomach, eyes, nose, as well as the symmetry of the structure of the face.

In general, everything that is visualized with the help of an ultrasound examination is subjected to analysis. In addition to studying the main characteristics of the development of the baby, experts check:

• how the placenta is located;
• the thickness of the placenta and the degree of its maturity;
• the number of vessels in the umbilical cord;
• condition of the walls, appendages and cervix;
• quantity and quality of amniotic fluid.

Norms for ultrasound screening of the 2nd trimester of pregnancy:

Deciphering the triple test (biochemical blood test)

In the second trimester, experts pay special attention to three markers of genetic abnormalities, such as:

• chorionic gonadotropin- this is hormone produced by the fetal chorion;
• alpha-fetoprotein ( Further AFP) - this is plasma protein (protein), initially produced yellow body, and then produced fetal liver and gastrointestinal tract;
• free estriol ( further hormone E3) is a hormone produced in placenta, as well as fetal liver.

In some cases, they also study the level inhibin (hormone) produced follicles). For each week of pregnancy, certain standards are established. It is considered optimal to conduct a triple test at 17 weeks of gestation.

When the level of hCG during the second screening is too high, this may indicate:

• about multiple pregnancy;
• about diabetes at mother;
• about toxicosis;
• about the risk of developing down syndrome if the other two indicators are below normal.

If hCG, on the contrary, is lowered, then this says:

• about ectopic pregnancy;
• about risk Edwards syndrome;
• about frozen pregnancy;
• about placental insufficiency.

When AFP levels are high, there is a risk of:

• anomalies in development kidney;
• defects neural tube;
• duodenal atresia;
• developmental disabilities abdominal wall;
• damage brain;
• oligohydramnios;
• fetal death;
• spontaneous miscarriage;
• occurrence Rhesus conflict.

Decreased AFP can be a signal:

• Edwards syndrome;
• diabetes mothers;
• low location placenta.

At a low level estriol great risk:

• development anemia in the fetus;
• adrenal and placental insufficiency;
• spontaneous miscarriage;
• availability down syndrome;
• development intrauterine infection;
• delays in the physical development of the fetus.

It should be noted that at the level hormone E3 some medications (eg. antibiotics), as well as improper and unbalanced nutrition of the mother. When E3 is elevated, doctors diagnose diseases kidney or multiple pregnancy, and also predict preterm birth, when the level of estriol rises sharply.

After the expectant mother goes through two stages of the screening examination, doctors analyze the information received using a special computer program and calculate the same MoM coefficient as in the first study. The conclusion will indicate the risks for a particular type of deviation.

Values ​​are given as a fraction, such as 1:1500 (i.e. one in 1500 pregnancies). It is considered normal if the risk is less than 1:380. Then the conclusion will indicate that the risk is below the cut-off threshold. If the risk is higher than 1:380, then the woman will be referred for additional consultation with geneticists or offered to undergo invasive diagnostics.

It is worth noting that in cases where the biochemical analysis corresponded to the norms during the first screening (indicators were calculated HCG and PAPP-A), then for the second and third time it is enough for a woman to do only an ultrasound.

Third screening during pregnancy

The last screening examination of the expectant mother takes place in third trimester. Many people wonder what they look at at the third screening and when this study should be done.

As a rule, if a pregnant woman was not diagnosed with any abnormalities in the development of the fetus or during pregnancy at the first or second examination, then she only has to undergo an ultrasound examination, which will allow the specialist to draw final conclusions about the condition and development of the fetus, as well as his position in the womb.

Determining the position of the fetus ( head or breech presentation) is considered an important preparatory stage before childbirth.

In order for the delivery to be successful, and the woman to give birth on her own without surgical intervention, the child must be in the head presentation.

Otherwise, doctors plan a caesarean section.

The third screening includes procedures such as:

• ultrasound, which is passed by all pregnant women without exception;
• dopplerography is a technique that focuses mainly on the condition of the vessels placenta;
• cardiotocography- a study that allows you to more accurately determine the heart rate of a child in the womb;
• blood biochemistry, during which attention is focused on such markers of genetic and other abnormalities as the level hCG, α-fetoprotein and PAPP-A.

Timing of the third screening during pregnancy

It is worth noting that only the doctor decides how many weeks 3 the screening should be done by a woman, based on individual features this particular pregnancy. However, it is considered optimal when the expectant mother undergoes a planned ultrasound at 32 weeks, and then immediately passes a biochemical blood test (if indicated), and also undergoes other necessary procedures.

However, for medical reasons, dopplerography or KTG fetus can be from the 28th week of pregnancy. third trimester starts at 28 weeks and ends with childbirth at 40-43 weeks. The last screening ultrasound is usually prescribed at 32-34 weeks.

Deciphering ultrasound

At what time the third screening ultrasound passes a pregnant woman, we found out, now let's talk in more detail about the decoding of the study. When performing an ultrasound in the third trimester, the doctor pays special attention to:

• for the development and construction of cardio-vascular system child, to exclude possible developmental pathologies, for example, heart disease;
• for proper development brain, organs of the abdominal cavity, spine and genitourinary system;
• to those in the cranial cavity vein of Galen, which plays an important role in the proper functioning of the brain to eliminate aneurysm;
• on the structure and development of the face of the child.

In addition, ultrasound allows a specialist to assess the condition amniotic fluid, appendages and uterus mothers, and check degree of maturity and placenta thickness. In order to exclude hypoxia and pathologies in the development of the nervous and cardiovascular systems, as well as to identify the features of blood flow in uterine vessels and the child, as well as in the umbilical cord, carry out dopplerography.

As a rule, this procedure is carried out only according to indications simultaneously with ultrasound. In order to exclude fetal hypoxia and define heart rate, carry out KTG. This type of research focuses solely on the functioning of the baby's heart, so cardiotocography prescribed in cases where the doctor has concerns about the condition cardiovascular child systems.

Ultrasound in the third trimester of pregnancy allows you to determine not only the presentation of the child, but also the maturity of his lungs, on which the readiness for birth depends. In some cases, to save the life of the child and the mother, hospitalization may be required for the purpose of early delivery.

According to the results of a biochemical blood test MoM factor should not deviate from the range from 0.5 to 2.5. The importance of risks for everyone possible deviations should correspond to 1:380.

Screening (from the English "screening") in medicine is called a complex of diagnostic procedures of a preventive orientation. It provides for the examination of a group of persons, united by a certain attribute, in order to identify and prevent any pathologies. A separate category of such patients are pregnant women. For early detection of the risk of developing genetic abnormalities, deviations from the normal course of pregnancy, monitoring the health of mother and child, a scheme has been developed that consists of three prenatal screenings.

We'll start over. Screening of the 1st trimester is the first stage of the regulation of comprehensive monitoring of the course of pregnancy. What examinations are included in the diagnostic program? When is the best time to go through them? And, most importantly, why is it needed? The answers to these and other questions are in the article.

In accordance with the regulations of the Ministry of Health of the Russian Federation, all pregnant women are strongly recommended to undergo prenatal, that is, prenatal, screenings three times - in each of the trimesters.

According to the accepted methodology, the first trimester according to the calendar method of calculation (from the moment of conception) is 14 weeks, according to obstetrics (from the date of the beginning of the last menstruation) - 12 weeks. The screening program at this time includes the first ultrasound and a laboratory biochemical blood test.

What they look at or what the first screening shows

The task of the first ultrasound screening is to assess the correct development of the embryo and the general condition of the mother. To do this, the necessary measurements are taken, the degree of development of organs is determined, and they are compared with indicators that correspond to the norm. During the examination, the following characteristics of the fetus are analyzed:

• KTP (coccyx-parietal size);
• length and symmetry of paired tubular bones - shoulders, forearms, thighs, lower legs;
• TVP (collar zone thickness);
• head circumference, BDP (biparietal size) and distance from the forehead to the back of the head;
• the stage of formation of the cranium, the symmetry of the cerebral hemispheres, its structure;
• size, structure and location of the heart, major blood vessels, heart rate (heart rate);
• the size of the abdomen, the correct development of the organs of the gastrointestinal tract, their position.

Ultrasound allows you to assess the condition of the reproductive organs of a woman:

• placenta - its structure, maturity, location;
• umbilical cord, vessels in it;
• amniotic waters, their quantity;
• uterus, its tone;
• cervix and internal os.

What is fetal KTR

One of the most important basic indicators of the correct intrauterine development of a child is KTR - coccygeal-parietal size. It is equal to the distance from the parietal bone to the coccyx and gradually increases with the development of pregnancy. There are tables that present the average values ​​​​of this parameter, which are equal to the norm. A slight deviation does not necessarily indicate the presence of pathologies, it may be an individual physiological feature.

If the measurements showed an increased CTE, this may indicate a large fetus, on the basis of which doctors predict the birth of a child weighing more than a median of 3-3.5 kg. But a significant lag of this indicator from the norm is a symptom:

• frozen pregnancy. When it is detected, immediate measures are taken to interrupt it in order to prevent dangerous consequences - infection, bleeding, further infertility;
• insufficient production of hormones by the woman's body, which is fraught with self-abortion. To normalize the hormonal background, corrective drug therapy is prescribed;
• infection with infectious diseases;
• genetic abnormalities in the development of the fetus. In order to confirm or refute such assumptions, it is necessary to undergo an additional examination.

Sometimes the deviation is associated with an incorrectly determined gestational age. To resolve this issue, a second ultrasound scan is performed after 7-10 days.

What is PAPP-A

The biochemical test of maternal serum in the first trimester involves the determination of the blood levels of two elements: PAPP-A and hCG.

PAPP-A (from the English “pregnancy associated plasma protein A”, or plasma protein A associated with pregnancy) is a specific protein produced by the placenta and allows drawing conclusions about the normal development of the fetus based on a comparison of the detected content with the prescribed one at the appropriate time.

PAPP-A is an important marker for many genetic pathologies. So, if its overestimated value most often indicates an incorrectly determined gestational age, then an underestimated one may indicate the risk of having a baby with Down syndrome, regressing pregnancy and the threat of spontaneous miscarriage.

human chorionic gonadotropin

HCG, or human chorionic gonadotropin, is a specific hormone that begins to be produced by the chorion just a few hours after conception. On the 12th day, its concentration increases by 2-3 times and reaches its peak at the 11th ... 12th weeks, increasing several thousand times compared to the value inherent in a non-pregnant woman. It is on the calculation of hCG that the action of all rapid tests is based.

Exceeding the average hCG level is expected in multiple pregnancies if the expectant mother is sick diabetes or suffering from toxicity. In other cases, this fact should alert, because it may indicate the risk of having Down syndrome. Reduced hCG is a sign of placental insufficiency, a risk of miscarriage and a marker of Edwards syndrome.

How to prepare for your first pregnancy screening

The first screening is the first important step in monitoring the course of pregnancy. Its results will make it possible to draw a conclusion about the condition of the mother, the development of the fetus, the presence or absence of pathologies. In this regard, it is extremely important to obtain objective results. There are rules that must be followed in order to achieve the maximum information content of examinations, including adherence to a special diet, fluid intake, and so on.

What tests does it include?

The program of the first screening includes two studies: ultrasound and a biochemical blood test.

Depending on how the ultrasound scan will be performed, the amount of fullness of the bladder depends. If the procedure will take place transvaginally, that is, with the introduction of a sensor into the vagina, no preparatory measures are required. And the transabdominal technique (through the anterior abdominal wall) involves taking a large amount of fluid (at least 0.5 liters) and a ban on going to the toilet for 4 hours before the diagnosis. No other preparation is needed for the 1st trimester ultrasound screening.

The material for the biochemical test is venous blood, which is taken on an empty stomach. In order to increase the accuracy of the study, it is recommended to follow a diet at least a day before the test.

Can I eat before screening

In order to undergo the first ultrasound, it is not necessary to limit yourself in nutrition. It is enough to observe the mode of drinking liquids.

The situation is different with the biochemical test. In addition to the fact that blood is taken on an empty stomach, it is important to follow a special diet the day before (preferably a few days before). It consists in the exclusion of products:

• contributing to an increase in cholesterol - too fatty, spicy, fried foods;
• containing known and potential allergens - citrus fruits, chocolate, nuts, seafood and the like.

How many weeks do the first ultrasound during pregnancy

In order to pass the first screening, there are strict time limits. The timing of its implementation is the period between the 11th obstetric week and the 13th plus 6 days. Diagnostics performed earlier or later is meaningless due to low information content.

This time range was not chosen by chance. The 12th week is the period when the embryonic period passes into the fetal period, and it is better to do an ultrasound at the very moment of this transformation. Analyzing the parameters inherent in this process, doctors will be able to draw objective conclusions.

At the same time, you need to go for blood donation, because the results of its analysis will supplement the information obtained during ultrasound scanning - they will confirm, refute, and reveal new facts.

How is the first screening done?

In order not to be afraid of the notorious prenatal screening, you need to understand how it goes. After a preliminary examination by a doctor, the patient is sent for the first ultrasound, and only then does a blood test. Let's consider these steps.

Exploratory survey

At the preparatory stage, the attending physician conducts a conversation with the patient to identify a hereditary predisposition to the occurrence of genetic abnormalities, collects an anamnesis of past diseases and a history of previous pregnancies, asks other questions that allow the woman to be classified as at risk (bad habits, taking pharmaceuticals, family relationships with her father). child, etc.).

Ultrasound procedure

Usually prenatal ultrasound screening of the 1st trimester is carried out transvaginally. In this case, the patient removes all clothing below the waist, comfortably sits on the couch and bends her knees. The diagnostician inserts a small probe, protected by a special condom, into the vagina and gently moves it. The procedure is absolutely safe and does not cause pain or discomfort.

Rarely, the examination is performed abdominally. In this case, the woman releases her stomach and lies down. The doctor lubricates the skin with a medical gel, which ensures continuous contact and eliminates the occurrence of an air gap between the sensor and the surface of the area under study. During the procedure, the sonologist moves a scanning device along the outer surface of the abdominal wall, and the information is transmitted to the computer screen.

In both the first and second cases, the procedure lasts only a few minutes, and the description is handed out immediately.

Biochemical screening

With the conclusion of the ultrasound on the hands, you can donate blood for biochemistry. These documents contain information about the exact gestational age, which was determined and confirmed by scanning. This information is very important for the subsequent comparison of the concentration of the studied elements of blood plasma with normal ones, since specific values ​​are inherent in each week.

If the ultrasound showed a regressing pregnancy or its fading, it is not advisable to undergo the second stage of screening.

Biomaterial sampling takes place in laboratory conditions. To perform the test, 10 ml of venous blood is needed. The results will be ready in a few weeks.

Service cost

If a pregnant woman is officially registered with the state antenatal clinic, all examinations will be free of charge for her.

If you wish to take advantage of the latest advances in medicine and undergo diagnostics using modern equipment and using more advanced reagents, you can contact a paid clinic. The first scheduled ultrasound and a biochemical test with the determination of all hormones during pregnancy will cost at least 4 thousand rubles. If you perform examinations separately, then the average price of ultrasound is 2,000 rubles, hCG analysis - 700 rubles, PAPP-A - 900 rubles.

What values ​​are considered normal

The main goal pursued by screening 1 is to confirm the correct development of pregnancy, not complicated by pathologies. To do this, the anatomical structures of the mother and fetus are studied, the main fetometric characteristics are measured, the concentration of important blood plasma components is determined and compared with the average ones.

One of the key indicators of the normality of intrauterine development is the previously mentioned KTR. Its norms depending on the period are given in the table.

Biparietal embryo size (BDP)

Another important fetometric parameter is BDP. To determine it, it is necessary to measure the distance between the parietal bones of the child's head. With its help, you can not only verify the correct development of the fetus, but also draw conclusions about the method of delivery, because the size of the skull may simply not correspond to the birth canal of the mother.

Heart rate (HR)

Heart rate is an important characteristic that is monitored throughout pregnancy. In some cases, the life of the child depends on the timeliness of identifying deviations. It is by this parameter that one can judge the presence of heart defects.

The heart muscle begins to work as early as the 3rd week after conception, but you can hear its contraction only at the 6th week. The rhythm of the fetal heartbeat at this stage coincides with the pulse of the mother. Over time, the myocardium contracts more and more often and reaches its peak at the 9th week with 175 beats per minute.

Collar zone (TVP)

TVP (collar space thickness) is another of the indicators that must be determined. In this oblong fold, which forms at the junction between the baby's neck and his body, fluid accumulates at the initial stages of development, which eventually disappears. Excessive swelling of this zone is one of the most objective markers of most trisomies (the appearance of an extra chromosome in one of the pairs of a row) and monosomies (lack of one chromosome in a pair). A thinning of the neck fold is also considered a deviation.

nasal bone

The tasks of ultrasound for pregnancy, which is scheduled for the 1st trimester, include monitoring the formation of the nasal bone of the child. At this point, she has not yet ossified. Therefore, on the 11th week, it is only important to make sure that it is present, and already from the 12th week - you need to measure it.

Incorrect development of this part of the skull indicates the presence of genetic abnormalities. It is her flattened shape with great confidence that gives the right to assume the development of Down syndrome.

For a period of 12-13 weeks, the size of the nasal bone should reach 3 mm. Deviations in the range of 2.0-4.2 mm are allowed.

Norms of a biochemical blood test

Biochemical analysis of maternal blood serum is the second, and no less important, stage of prenatal screening. Its results help confirm or refute the preliminary conclusion of an ultrasound scan, as well as detect a number of other pathologies. The study program includes the determination of plasma concentrations of hCG and PAPP-A.

Norm of hCG and free β-subunit of hCG, comparative tables

Immediately, we note that hCG and the free β-subunit of human chorionic gonadotropin are different indicators. Moreover, it is the second one that is considered more informative as a marker of fetal chromosomal diseases, in particular, Down syndrome.

Depending on the gestational age, the following values ​​\u200b\u200bof hCG and the free beta subunit of hCG are considered normal.

PAPP-A norm in the comparative table

PAPP-A is a specific protein produced by the placenta, the content of which in the blood plasma constantly increases during pregnancy. Its concentration can be judged harmonious development a child, and its deviation from the norm speaks of various pathologies, including genetic ones, as well as the threat of miscarriage.

In different laboratories, the norms, expressed in mU / ml, may differ when determining the hormone and plasma protein. It is recommended to start from MoM - a coefficient showing the degree of deviation of the results from the norm. The allowable range is 0.5-2 MoM.

Deciphering the results

After the pregnant woman has undergone ultrasound and biochemical screening of the 1st trimester, doctors begin to decipher the information received. For this, a unified method for calculating the risks of pathologies, including genetic ones, has been developed. Calculations are made according to the basic and individual algorithms. To eliminate the possibility of error and improve the accuracy of the results, special certified software systems are used, one of the most popular of which is PRISKA.

Factors affecting the results of the first screening

There are a number of objective factors that affect the results obtained during the first screening:

• conception by IVF method. Ultrasound - increased LZR, biochemistry - increased hCG, decreased PAPP-A (by 10-15%);
• twin pregnancy. Probably a general distortion of the results. Usually - an increase in the concentration of β-hCG;
• overweight pregnant. Biochemistry - elevated hCG. With insufficient weight, the opposite situation is observed;
• diabetes. Biochemistry - elevated hormone levels;
• the amniocentesis procedure (invasive analysis of amniotic fluid) performed the day before. Biochemistry - unreliable results are possible;
• stress experienced the day before, unstable mental condition future mother. Unpredictable distortion of survey results.

False results

At the time of the first screening, the baby in the womb is still very small. In this regard, it can be difficult to consider the details of the structure of his body, to make the necessary measurements. According to statistics, studies performed in the early stages have the maximum error. For example, the efficiency of detecting chromosomal abnormalities according to the results of ultrasound and blood tests is estimated at 86%, while false positive results occur in 6%.

How to confirm or refute the results

The final screening form contains complete information, including a description of the results obtained, risk assessment (age-related and in the context of diseases), and the final MoM coefficient. Based on this document, the doctor observing the pregnant woman draws conclusions about further actions.

If the patient believes that unreliable results were obtained during the examinations, she can be re-diagnosed in another medical institution. To do this, you should not only pass tests, but also undergo an ultrasound scan. It makes sense to do this before the 14th obstetric week.

Deviations

The first ultrasound and blood plasma analysis, subject to the deadlines for their implementation, can reveal the following deviations:

• Down syndrome. The chance of an extra chromosome in the 21st row is 1:700. Thanks to timely diagnosis, this probability has decreased to 1:1100;
• Edwards syndrome. Another type of trisomy, already in the 18th chromosome row. Occurs in one in 7,000 babies;
• Patau syndrome. A dangerous mutation caused by the third chromosome in the 13th row. Probability - 1:10 000;
• Smith-Opitz syndrome. Caused by a failure in the synthesis of organic substances, followed by metabolic disorders;
• Cornelia de Lange syndrome. It is characterized by multiperverse symptoms;
• pathologies of the development of the neural tube (meningocele, anencephaly and the like);
• pathologies of the abdominal cavity, including omphalocele, that is, a hernia of the anterior wall, umbilical hernia, and others.

ultrasound

It is possible to suspect deviations in the development of the fetus and the course of pregnancy if the fetometric characteristics obtained during ultrasound differ from normal ones, and not only the module, but also the sign of discrepancies plays a role.

1. KTR. More than normal- a large fruit, the term is incorrectly set; less than normal - abnormal development of pregnancy, insufficient production of hormones by the mother's body, an infectious process, genetic abnormalities.
2. BPR. More than normal - cerebral hernia, tumor, hydrocephalus, as well as the large size of the fetus (subject to proportions); less than the norm - developmental delay.
3. heart rate. Any deviation indicates heart disease.
4. TVP. The discrepancy in the thickness of the neck fold is a sign of a change in the karyotype according to the type of Down, Edwards, Patau, Shereshevsky-Turner syndromes.
5. Nasal bone. Its absence or small size is a sign of most trisomies.

What if hCG is not normal

An increased level of hCG in the blood plasma most often indicates the risk of having a child with Down syndrome. However, this phenomenon is inherent in women with diagnosed diabetes mellitus, suffering from toxicosis and with multiple pregnancies.

An unusually low level of hCG is a sign of Edwards syndrome. Lack of production of this hormone can also signal problems with the placenta - placental insufficiency and the risk of miscarriage.

What if PAPP-A is abnormal

A low protein content in the blood signals not only the threat of spontaneous abortion, but also the presence of chromosomal abnormalities (Down, Edwards, de Lange syndromes).

In rare cases, an increase in protein concentration is observed. Usually this fact has no diagnostic value. Women with elevated PAPP-A are no more likely to develop complications than those with normal protein levels.

double test

All screening programs (in the first, second or third trimester) include a biochemical analysis of maternal serum. Each period of pregnancy has its own special properties, including changes in the composition of the blood.

In the first trimester, the maximum amount of information is given hCG levels and RAR-A. According to the number of elements studied, such a test is called a double test. Already in the second trimester, in addition to ultrasound, a triple test is taken (hCG, alpha-fetoprotein, free estriol), less often a quadruple test, which also includes inhibin A.

MoM

In order to standardize the summing up of screening results, which, in turn, avoids the influence of human and other external factors when assessing the risk of developing pathologies in the fetus, the MoM coefficient (multiple of median) is used in medical practice. It shows the ratio of the obtained results to the median. Its ideal value is "1". Deviations are allowed in the range from 0.5 to 2.5.

This coefficient correlates with objective factors that directly affect one or the indicator, for example, age, race, bad habits, concomitant diseases, experience of previous pregnancies, IVF, and so on.

What does it say about Down Syndrome?

Down syndrome, or trisomy 21, is the most common genetic disorder. It is quite successfully diagnosed already at 11-13 weeks of gestation. The main marker of such a pathology on ultrasound is a thickening of the cervical fold. If TVP exceeds 3 mm, then the probability of having a child with Down syndrome is very high. Additional signs:

• absence of the nasal bone after the 11th week. Only 2% of healthy children have such a symptom and 60-70% have Down syndrome;
• moderately reduced skull, flat occiput, three fontanelles;
• small maxillary bone;
• smoothness of facial features;
• violation of blood flow, including in the reverse direction, in the duct of Arantia. It is observed in 5% of healthy and 80% of sick children;
• tachycardia (rapid heartbeat);
• hypotonic muscle tone;
• bladder enlargement;
• absence of one of the umbilical arteries;
• elevated hCG levels, reduced - PAPP-A.

How to recognize Edwards syndrome

Edwards syndrome is less common than the deviation described above, but its consequences are much more serious. 90% of children born with this pathology do not live up to a year. This trisomy can be identified by the following signs:

• absence of a nasal bone;
• reduced skull with protruding occiput;
• slowing of the heartbeat;
• hypertonic muscle tone;
• omphalocele;
• single umbilical artery;
• reduced levels of hCG and PAPP-A.

What is risk and how is it calculated

Based on the results of ultrasound and blood tests scheduled for the 1st trimester, using a special software package with built-in calculation algorithms, the risk of developing a particular pathology for a particular pregnancy is determined. The conclusion regarding the probability is expressed in the form of a fraction, for example, "trisomy 21 base risk - 1:350". This means that if you take 350 patients with similar indicators, then one of them will have a child with Down syndrome.

A good conclusion is given if the risk does not exceed 1:380. If it is in the range of 1:250…1:380, then it is considered high. If the probability of having a baby with a pathology exceeds 1:250, the question arises of terminating the pregnancy.

What to do if a high risk is identified

If the patient has a confirmed high risk of having a child with diseases caused by genetic mutations, a consultation with a geneticist is necessary. Having studied the examination materials, he can prescribe repeated ultrasound or blood biochemistry, as well as invasive forms of diagnosis: chorionbiopsy, cordocentesis or amniocentesis. Based on a set of information, the issue of maintaining or terminating the pregnancy will be decided.

What to do if the doctor says you need an abortion

Unfortunately, in some cases there is almost one hundred percent certainty in the birth of a sick child, especially if this is confirmed by additional examinations. If the doctor recommends, or even insists, on interruption, then most likely he has a good reason for doing so. In any case, only the pregnant woman makes the final decision.

Further actions

If the first ultrasound and plasma biochemistry were successful, demonstrated an excellent condition of the mother, confirmed the planned development of a healthy child, then the next scheduled screening will take place in the second trimester (between the 16th and 20th weeks). In this time period, a pregnant woman should visit her gynecologist every two weeks and regularly take general blood and urine tests.

Examination of the state of the growing embryo for the detection of chromosomal abnormalities, the prognosis of the development of pregnancy is carried out at the first screening during pregnancy. How it is done, what results are considered acceptable - is determined by the ultrasound doctor, geneticist, biochemist.

The correct calculation of the gestational age helps to determine not only the expected date of birth. It is necessary for planning the first screening. By the beginning of the 11th week, the embryonic period of development ends. Formed organs, limbs, facial bones appear, the nervous system is formed.

Screening of the first trimester of pregnancy is carried out by the end of the term. The allowable completion date of the study is 13 weeks and 6 days.

It is useless to screen before these dates: the picture of pathologies may be distorted and will not lead to the detection of pathologies.

Features of the first screening examination

The difference in the first screening examination is the use of a transvaginal method for introducing an ultrasound probe. This method is carried out by inserting a sensor into the vagina.

Transvaginal ultrasound is performed only in the 1st trimester of pregnancy. By the 16th week, the height of the uterus noticeably increases, the fetus becomes larger, which allows for examinations of the 2nd, 3rd screening to be limited only to the transabdominal method.

Preparation for the examination

The fat layer, accumulated gases in the intestines, can interfere with a clear view of the fetus and uterus during a transabdominal examination. To eliminate the causes, it is necessary to prepare within 2 - 3 days.

It is necessary to refuse foods high in fiber, which can increase gas formation. The procedure must be carried out on a full bladder. To do this, before starting the study, it is recommended to drink 1 - 1.5 liters of water without gases.

Blood sampling for hCG hormones, PAPP-A is performed on an empty stomach, with a preliminary rejection of fried, fatty, sweet foods for 2 to 3 days. Compliance with the diet is not important, but it will allow you to more accurately reveal the picture of the hormonal background of the mother and fetus.

How the examination is carried out

The first screening during pregnancy, as they do, is decided by the doctor based on the specified gestational age. Contact of the sensor with the body is facilitated by a special gel based on glycerin, which is applied to the skin. Uterus with existing amniotic fluid actively conducts sounds.

This allows you to study the development of the fetus, listen to its heartbeat, register pathologies of organs and systems. The awkward position of the fetus in the uterus can make a comprehensive examination difficult. In this case, the woman needs to provoke the child to change the position with light active movements.

The survey is carried out in 2 stages:

Ultrasound - research:

Test for hCG hormones, PAPP-A. If high risks of fetal pathology are detected, an additional examination of amniotic fluid and placental cells is prescribed.

Goals of the first screening

The purpose of 1st trimester screening is to:

• Determining the timing of pregnancy.
• Clarification of the compliance of the size of the fetus with developmental standards.
• Identification of pathologies of the bone, cardiovascular, system, gastrointestinal tract.
• Detection of genetic diseases - syndromes. Down, Edwards.
• Exclusion of other possible malformations.
• Monitoring of the placenta.
• Condition, readiness of the uterus for bearing.

According to the results of test studies, a conclusion is made about the condition of the fetus, a prognosis is given for the further development of pregnancy. Early detection pathologies allows you to pay attention to possible risks, to prevent the further development of complications.

Severe complications that threaten the life of the mother and give reason to recommend artificial termination of pregnancy in the early stages.

Ultrasound norm indicators - research

Prenatal screening is considered harmless to mother and baby. Comparison of the obtained indicators with the standards gives the most complete picture of the condition and risks of pregnancy.

Main characteristics:

• KTR (coccygeal - parietal size). The length of the fetus from the crown to the coccyx should be from 43 to 85 mm. A decrease in the length of the fetus indicates a slow development, or genetic pathology.
• BDP (biparietal size). Determined by the distance from temple to temple. Changes in BDP data indicate pathologies of the brain.
• TVP (collar space thickness). An increased indicator requires an in-depth analysis for the detection of Down syndrome, Edwards.
• The length of the nose bone. Research indicators range from anatomical structural features to genetic pathologies.
• HR (heart rate). A noticeable decrease or increase in heart rate indicates possible violations of the brain, defects in internal organs.
• The size of the chorion, amnion and yolk sac. At the first stage of fetal development, they are the basis of the placenta, which is necessary for normal pregnancy. The wrong location of the chorion threatens miscarriage. Amnion indicators are necessary for the study of amniotic fluid. The yolk sac is a nutrient medium for the development of internal organs. Its absence or minimal presence indicates the dynamics of the development of pregnancy.

Collar thickness

The thickness of the collar space (NTP) is an important indicator of the risk of chromosomal diseases. Collar space - subcutaneous fluid that accumulates between the outer surface of the skin and bone tissue.

How to do the first screening during pregnancy in order to exclude incorrect results depends on the qualifications of the gynecologist. It is important not to be mistaken in determining the gestational age required for this study. Fetal size at 10 weeks is insufficient for testing. By 14 weeks, the size of the cervical fold is physiologically reduced.

There are conditions that must be observed to obtain the most correct result:

• Accurate determination of the gestational age. It is determined by the size of the coccyx-parietal zone.
• The lateral position of the embryo allows you to most clearly determine the data of the test. The inability to achieve the correct position of the fetus gives reason to use the transvaginal method of research.
• Physician competence. Loops of the umbilical cord, amniotic cavities can give positive results. An experienced doctor using high-precision equipment should exclude false positive results.

A complete picture of the state of the embryo is given not only by ultrasound data - studies, but also by the analysis of biochemical markers. Test results may vary at different stages of pregnancy. The general boundaries of the examination of the fluid of the collar fold should vary from 0.7 mm to 4 mm.

An increase in TVP data gives grounds for an in-depth examination, which includes the study of amniotic fluid, placenta, cord blood.

nasal bone

A short nasal bone does not always mean a pathological condition of the embryo. A noticeable decrease in its length, combined with positive results of TVP, give grounds to define pregnancy as pathological. A serious developmental disorder is nasal aplasia - its complete absence.

At the lower limits of the screening period, only the presence or absence of the nasal bone is detected. 12 - 13 weeks of pregnancy allows you to specify the size of the nose bone in numerical values. Permissible limits are from 2 to 4.2 mm. Small deviations may indicate the anatomical features of the unborn child.

A significant decrease in the indicator indirectly indicates chromosomal abnormalities. However, these data are not enough for a definitive diagnosis. The conclusion about the presence of severe genetic defects is possible only with additional deep monitoring of the fetus and mother.

Heart rate

The heart rate of a healthy fetus should match developmental parameters. The indicator is correct, subject to compliance with the KTR data. The size from the coccyx to the crown must be at least 8 mm. Only in this case can we talk about the recommended heart rate indicators. As the fetus grows, they decrease.

If at 9-10 weeks the heartbeat is 170-190 beats per minute, then by the 13th week it drops to 160 beats. Small deviations are physiological errors and do not pose a danger. The absence of a heartbeat indicates a missed pregnancy. Repeated ultrasound, additional studies will be able to confirm or refute the presumptive diagnosis.

A decrease in heart rate of less than 100 beats per minute may indicate Edwards syndrome.

Increased heart rate up to 200 beats per minute - dangerous symptom Patau syndrome. Heart rate markers are not decisive for the diagnosis of chromosomal diseases. They indicate the risks of developing pathologies. Comprehensive monitoring of all organs and systems is designed to give a complete prognosis of pregnancy.

Biparental size

Biparental size means digital measurements of the width of the fetal head from temple to temple. BDP is the main indicator of the development of the brain of an unborn child.

The indicators can also serve as the basis for specifying the gestational age and, in some cases, determining the method of physiological childbirth. With a large size of the child's head, the question of planned caesarean section.

The rate of BDP at 11 - 13 weeks of development should be in the range from 13 to 28 mm. Going beyond the limits of the norm is allowed, subject to a proportional increase in all indicators - KTR, TVP, nasal bone. This indicates the large size of the fetus. Slightly elevated BDP, while the rest of the markers correspond to the norm, levels off by the end of 14 weeks.

A noticeable increase in the indicator indicates the presence of brain pathologies that are incompatible with life.

The minimum dimensions of the BDP indicate underdevelopment of the hemispheres or the absence of brain segments. Severe malformations are not amenable to treatment, the perinatal prognosis is unfavorable. The choice of terminating or leaving a pregnancy is made by the woman herself.

Norms of hormones that are determined by the first screening (hCG, PAPP-A)

The biochemical stage of prenatal screening is to study the levels of hCG hormones, PAPP-A. Blood markers for determining the level of hormones are a necessary element in the study of fetal development.

Chorionic gonadotropin is responsible for the normal course of pregnancy and consists of two units - α and β. The hormone is responsible for stimulating the production of hormones, the gonads. Its amount increases by 9-10 weeks, and then, the concentration decreases. The norm corresponds to 17 - 114 mIU / ml.

An increase in hCG indicates the risk of detecting genetic pathologies - Down syndrome. A downward change puts pregnancy at risk for detecting Edwards syndrome, developmental delay, and fetal death.

The purpose of determining the level of the PAPP-A hormone is to identify chromosomal pathologies - Down syndrome, Edwards, Cornelia de Lange, the risk of miscarriage. The normative indicator varies from 0.45 to 6.0 mU / ml. A significant decrease in the value in numerical terms indicates the need for additional research, the appointment of an in-depth triple test.

What pathologies can be detected by the first screening? (Down syndrome, Edwards syndrome, Patau syndrome)

The first screening makes it possible to monitor the condition of the fetus, identify future pathologies of physical and mental development. Comparison of indicators of biparental sizes, distance of the coccygeal-parietal zone, nasal bone, hormonal state give the most accurate predictions of fetal development and current pregnancy.

Genetic disorders are associated with chromosomal abnormalities - trisomy. It is characterized by the presence of a triple pair of chromosomes instead of two.

Risk calculation at first screening

The totality of the data of the first screening gives the most complete picture of the course of pregnancy. Predictions, decisions to prolong pregnancy is a serious issue. You should carefully consider the examination process and test results.

Numerical values ​​of biochemical analysis may differ depending on the research methods of laboratories. It is recommended to conduct screenings in one medical center, for the reliability of observation in a single measurement scale. It is important to consider how the first screening is done during pregnancy, what factors are taken into account when calculating the data.

The presence of pathologies may be the result of:

Survey data are expressed as proportions of risk in relation to the total number of similar results. For example, a fraction of 1:10,000 means: for 10,000 pregnancies with similar indicators, there is 1 risk of confirming the diagnosis.

A fraction with a smaller denominator is considered an unfavorable forecast. The probability of detecting an anomaly is higher in a pregnant woman with rates of 1:300 than 1:627.

The first pregnancy screening is done to influence the final medical report. A positive test result means a high risk of fetal pathology. To confirm or exclude it, it is necessary to undergo an additional study of the placental membrane, amniotic fluid, cord blood.

Can indicators be false?

There are factors that distort the results of the survey.

Anatomical features of the structure of a woman, subjective conditions of the body lead to false positive results:

The birth of a healthy child, despite the positive data of the examination, indicates the relative imperfection of the study, the influence of subjective factors on the examination process.

The first screening in pregnancy is thought to be affected by false negative results. It is a consequence of a defect in the examination methodology, low-quality reagents. The birth of a child with developmental anomalies with negative screening results refers to the percentage of statistical error, but it is a tragedy and a serious test for the family.

It is necessary to remember why and how the first screening for pregnant women is carried out. The procedure is planned, painless, affordable. Identification of the risk of detecting a genetic pathology is a reason for further in-depth examination. The decision to terminate the pregnancy or continue it, the woman takes on her own.

Video of the first screening

Pregnancy management. First screening:

11-13 weeks of pregnancy. Diary of a pregnant woman: