Screening in English means “sorting” - in fact, this examination plays the role of “sorting”, dividing pregnant women into those whose indicators fit into the normal range, and those who should do additional diagnostics. What kind of analysis is this, and what do they take blood for? Biochemical screening 1 trimester (specifically 11-13 weeks) is a set of diagnostic measures, consisting of ultrasound and a biochemical blood test.

It is used to identify the risk of developing severe fetal pathologies, as well as genetic abnormalities and severe congenital diseases.

The unknown is scary, so let's try to understand the concepts so that on the threshold of the biochemical part of the screening of the first third of gestation, we feel confident and competent.

A woman gives blood biochemistry twice for the entire period of bearing a baby - at terms of 11-13 weeks and 16-20 weeks. For this, venous blood is taken from the patient on an empty stomach.

What does it show?

The first screening is also called a “double test”, since two main indicators are determined during the analysis in the blood: hCG and PAPP-A. Let's try to figure out what each of them is.

Reference! Chorionic gonadotropin (more precisely, its free unit) is a hormone secreted by the cells of the chorion (embryonic membrane).

It is determined almost immediately after conception. This indicator increases, reaching the highest values ​​by the end of the first three months. Then the number that determines hCG decreases, stopping at one value after a certain gestational age.

Reference! PAPP-A is a protein secreted by the outer layer of germ cells.

During all nine months, its number should increase in proportion to the period. Functionally, PAPP-A is responsible for the immune response of the expectant mother during pregnancy, and also determines the development of the placenta and its normal functioning.

Video

The video below will help you get an idea of ​​what biochemical screening is and why it is done.

How do they do it?

Preparation for the first biochemical screening during gestation includes several stages:

1. The first ultrasound is required condition screening, because some analysis indicators will depend on the exact gestation period, which the ultrasound will show.
2. Blood from a vein is taken strictly on an empty stomach It's better not to drink. If you have a long wait, take a small snack with you, but you will be able to eat only after the blood sampling.
3. On the eve of the study (and preferably a few days before it), it is worth limiting your diet by excluding certain foods.

Diet

In order for the result of the biochemical part of the screening to be reliable, doctors recommend that patients follow a short-term diet on the eve of blood donation.

It is best to adhere to dietary restrictions already 3-5 days before the procedure.

Throughout the diet eliminate from the diet:

• industrial sweets, especially chocolate, gummies and multi-colored dragees;
• tea, coffee, cocoa;
• fish, especially red varieties;
• seafood;
• pickles, canned and smoked products;
• offal;
• meat.

If a woman is taking drugs that do not play a vital role, she should stop taking them a few days before donating blood.

In this case, it is necessary to consult a doctor.

Vitamins and certain other pharmaceuticals may interfere with test results.

This can cause a lot of unrest, unnecessary for the expectant mother.

Deciphering the results

A feature of such an indicator as hCG is its dependence on the gestational age.

Table 1. HCG norms.

Both promotion and decrease in hCG speaks of trouble in the development of the child or about some conditions of the mother. For example, during pregnancy with twins (triplets) or severe toxicosis, the indicators may not fit into the norm. An increase in hCG can be recorded with:

• multiple pregnancy;
• Down syndrome - the most famous of the forms of genomic pathology;
• severe course of toxicosis;
• the patient has diabetes.

Reduced hCG may indicate the presence of conditions such as:

• ectopic pregnancy;
• placental insufficiency;
• high risk of abortion;
• Edwards syndrome, which is characterized by many malformations.

We continue to decrypt: PAPP-A regulations and deviations from them

When literally deciphered from English, the concept of “PAPP-A” is translated as “A-plasma protein associated with the gestation process”. Its normal values ​​depend on the term.

Table 2. PAPP-A norms.

Abnormalities in the PAPP-A score have their own diagnostic value. An increase in the indicator indicates the bearing of several children, but a decrease may be the result of a number of factors:

• fading pregnancy;
• high risk of miscarriage;
• neural tube defect;
• some types of trisomy, the most famous of which was Down syndrome.

Despite the importance of the study, a diagnosis cannot be made based on the results of biochemical screening. Deviations in hCG and PAPP-A data become a reason for additional examination expectant mother. Blood biochemistry in the first trimester is shown to all women preparing for motherhood. The procedures are carried out at the request of the woman, and doctors do not recommend ignoring the prescribed examinations.

Risk group

There are patients for whom it is especially important to conduct biochemical screening, as they are in a potential risk group:

• age risk - pregnant women over 30 years old (when carrying the first child) and over 35 years old (when carrying the second and subsequent baby);
• women who have previously experienced several missed pregnancies or miscarriages;
• patients who self-administered in early pregnancy drugs that are dangerous for the normal development of the child;
• women who have been ill early dates gestation with infectious diseases;
• patients who have relatives with genetic malformations or diseases;
• women who have previously given birth to children with genetic abnormalities;
• pregnant women married to a close relative;
• patients exposed to radiation before conception or early gestation (or the spouse was exposed to such exposure);
• the conclusion of an ultrasound testifying to genetic abnormalities.

Norma MoM

Despite the fact that the first biochemical screening is called double, the attending physician determines three indicators. The result of the survey is largely assessed precisely by MoM - the coefficient responsible for the degree of deviation of the analysis data of a particular woman from the average statistical indicators.

Reference! Normal MoM - from 0.5 to 2.5 (when carrying several children - up to 3.5).

Where to do it and how much does it cost?

A doctor sends a pregnant woman for a biochemical analysis, and this procedure is free. But if she wants to undergo such an examination at her own discretion, screening in a private clinic will cost 5-9 thousand rubles.

Blood sampling takes place in the laboratory of a polyclinic, perinatal or diagnostic center.

Conclusion

Biochemical screening is an optional procedure, but it is highly recommended for any pregnant woman to perform. It is this analysis that makes it possible to detect albeit rare, but potentially possible deviations in order to make a difficult decision in time or start treatment procedures.

Screening - translated from English, this word means sorting or selection. In a word, perinatal screening is a special set of analyzes, tests, studies that can give a clear idea of possible deviations in the development of the unborn child.

The entire screening is divided into the number of trimesters, since during each period of gestation, the expectant mother must undergo the scheduled studies.

Screenings are divided into double, triple and quarter tests, demonstrating certain hormonal abnormalities in all periods of pregnancy.

The main goal of screening is the division of risk categories in the development of congenital malformations in the fetus: Down syndrome, Edwards syndrome, neural tube defects. According to the indicators of the ultrasound examination and the results of a blood test taken from a vein, the total is calculated.

Naturally, during the processing of information, the personal information of the woman is taken into account (from age, weight, bad habits to the use of hormonal drugs during pregnancy).

What tests should be taken for screening during pregnancy?

TVP is measured at strictly limited terms of pregnancy - from 11 to 14 weeks, more precisely - up to 12 weeks. Later, the fetus will grow up and the TVP indicators will lose their information content.

In the first trimester, blood is donated for the hormones b-hCG and PAPP-A.

The second screening (16-18 weeks) does not include ultrasound - the indications for it are taken from the first. And blood must be taken for the b-hCG hormone, AFP alpha protein and estriol - that is, the so-called "triple test".

Screening Test Results

Elevated hCG may indicate such abnormalities: chromosomal developmental defects, multiple pregnancy, Rh conflict. Reduced hCG talk about ectopic pregnancy, the threat of miscarriage, non-developing pregnancy. An increase and decrease in AFP indicates probable chromosomal abnormalities.
The sum and combinations of deviations in the proportions of hormones can also tell about the presence of pathologies. Suppose, with Down's syndrome, the AFP indicator is underestimated, and hCG, on the contrary, is overestimated. A hallmark of an open neural tube is an elevated level of alpha protein (AFP) and a reduced level of the hormone hCG. In Edwards syndrome, the studied hormones are lowered.

If there is a high risk

The geneticist will study your indicators, information about your pedigree, clarify whether hormonal treatment (Utrozhestan, Dufaston) was used to preserve the pregnancy and will definitely warn you that there is no way to know with 100% accuracy whether the baby has pathologies, except for invasive methods. They, these methods, are not very harmless: chorion biopsy, amniocentesis (taking by means of a puncture in the abdomen amniotic fluid), cordocentesis (puncture from the umbilical cord of the fetus). There is a certain risk in conducting invasive studies.

Unfortunately, to date, screenings carry little information. The unreliability and fallacy of non-invasive studies is quite high. Some doctors even argue about the advisability of such procedures.

Provides an opportunity to recognize pathologies in the development of the fetus. It consists of an ultrasound and blood tests. For diagnostics, all the personal data of a woman are taken into account (from age, weight, the presence of chronic diseases to bad habits). They take blood from a vein and do an ultrasound.

Timing of the first screening during pregnancy

All conclusions about the development of the unborn child are made based on the results of the sum of studies and analyzes. If the diagnosis has determined a high probability of anomalies in the formation of the baby, the woman is sent for amniocentosis and CVS.

Risk group:

• Women who are whiter than 35 years old.
• Those future mothers who had children with Down syndrome or other genetic anomalies in their family.
• Pregnant women who have already given birth to children with abnormalities or who have had miscarriages in the past.

Stage of preparation for the first screening

1. Try to conduct a blood test and ultrasound on the same day and in the same laboratory.
2. Do a blood test on an empty stomach, refrain from sexual intercourse to exclude the possibility of distorting the results.
3. Weigh yourself before you go to the clinic - this is necessary to complete the form.
4. Before the procedure, you should not drink water, at least not more than 100 ml.

How does the first screening process work?

The results of a blood test at the first screening do not provide authentic data for making a diagnosis, but give rise to additional studies.

Second phase- This is an ultrasound of the first three months of gestation. It determines the development of internal organs and the location of the limbs. In addition, measurements of the child's body are taken and compared with the norms corresponding to the period. This screening examines the location and structure of the placenta, the nasal bone of the fetus. Usually at this time it is visible in 98% of children.

Norms of the first screening during pregnancy

• If the results of the tests are above the norm, then the risk of Down syndrome in the unborn child is high. If they are below normal, then Edwards syndrome is possible.
• The PAPP-A norm is another coefficient of the first screening during pregnancy. This is plasma protein A, the level of which increases throughout pregnancy, and if this does not happen, then the unborn child has a predisposition to diseases.
• In the case when PAPP-A is below the norm, the risk of developing abnormalities and pathologies in the child is high. If it is above the norm, but at the same time the rest of the research results do not deviate from the norm, then you should not worry.

To calculate the indicators, you must use the MoM coefficient, which indicates deviations from the average. In the process of calculation, corrected values ​​are taken, taking into account the features female body.

If you have any doubts about the results of the screening, repeat it with the same blood tests and ultrasound in a different laboratory. This can be done before the 13th week of pregnancy.

Repeated screening is carried out during the second trimester, although the 16-17th week is considered the most effective.

Timing of the second screening during pregnancy

The second screening is of three types:

1. ultrasound (detection of anomalies using ultrasound),
2. biochemical (blood counts),
3. combined, where the first two are used.

- This is a biochemical study of the blood of the expectant mother according to certain tests.

More precisely, according to the so-called "triple test", according to which the degree of proteins and hormones is studied, such as: human chorionic gonadotropin (hCG) in the blood, alpha-fetoprotein (AFP), free estirol. The test becomes “quadruple” when this secondary set of studies also includes taking blood for the level of inhibin A.

The study of the concentration in the blood of these hormones and proteins makes it possible to judge with a high degree of probability the possibility of the formation of Down syndrome, Edwards syndrome, and neural tube defects in a child.

The conclusions of the repeated complex of studies can be an indirect indicator of the defective state of the formation of the child and exacerbations of the course of pregnancy. For example, an abnormal degree of hCG indicates abnormalities in the chromosomes, the risk of preeclampsia, or the presence of diabetes in the expectant mother.

Reduced levels of hCG may indicate a violation of the development of the placenta.

Elevated or decreased levels of AFP and inhibin A in the blood serum of a pregnant woman are a sign of a disorder in the natural formation of a baby and probable congenital anomalies - defects in the open neural tube, possibly Down syndrome or Edwards syndrome. If alpha-fetoprotein rises sharply, the fetus may die. With a change in the level of the female steroid hormone - free estriol, disturbances in the activity of the fetoplacental system can be allowed: its deficiency suggests probable malfunctions in the functioning of the child.

In the case when the results of the repeated complex of studies turned out to be unfavorable, one should not worry ahead of time. They only talk about the perceived risks of deviations, there is no final diagnosis. In the case when at least one component of the secondary screening does not fit into the norm, it is necessary to do an additional study. Several reasons may affect the indicators of the screening study: in vitro fertilization, the weight of the woman, the presence of diabetes, bad habits such as smoking.

Videos about screening

This type of examination is prescribed for women who are diagnosed with 11-13 weeks of pregnancy. The initial stage of the first screening during pregnancy is an ultrasound examination. After that, the pregnant woman is sent for a biochemical blood test.

Such events make it possible to identify genetic defects, pathologies in the structure of the embryo and respond to them in a timely manner.

How to prepare for the first screening?

The procedure under consideration includes two types of examination, each of which needs a certain preparation.

ultrasound

Can be done in two ways:

1. External (abdominal). It is given with a full bladder, therefore, 30-60 minutes before the start of the procedure, the pregnant woman must drink at least half a liter of purified water without gas, or not urinate 3-4 hours before the start of the ultrasound.
2. Vaginal. This type of examination does not require special preparation. Some clinics require patients to come to the appointment with their own diaper, sterile gloves and a condom for the ultrasound transducer. All this can be purchased at almost any pharmacy.

(double test)

It provides for the following preparatory measures, ignoring which can significantly affect the test results:

• 2-3 days before the analysis, a pregnant woman should refrain from fatty, salty foods (meat, seafood), citrus fruits and chocolate. The same goes for multivitamins.
• Blood must be donated on an empty stomach. The last meal should be at least 4 hours before the test.
• Doctors also advise to exclude sexual intercourse a couple of days before the screening.

How does the first screening in pregnant women go and what does it show?

The specified type of examination must begin with. After all, it is ultrasound diagnostics that makes it possible to determine the exact gestational age - and this very important for the second stage of screening: the double test. After all, the indicators of the blood norm, for example, for 11 and 13 weeks will be different.

In addition, if an ultrasound scan detects the fetal fading or the presence of serious anomalies in it, there will be no need for a biochemical blood test.

Thus, at the time of passing the second stage of the first screening, the pregnant woman should have the conclusion of an ultrasound doctor in her hands.

Ultrasound procedure

The type of examination under consideration favors the identification of such physical defects of the fetus:

• developmental delay.
• The presence of serious pathologies.

Also thanks to ultrasound the gestational age is determined, the number of fetuses in the uterus, the approximate date of birth is set.

In the first third of pregnancy, the following indicators are checked on an ultrasound machine:

1. The distance from the coccyx to the parietal part of the head. This parameter is also called the coccygeal-parietal size (KTR). At the 11th week of pregnancy, the CTE varies within 42-50 mm, at the 12th week - 51-59 mm, at the 13th - 62-73 mm.
2. The size of the nasal bone. At the 11th week, it is not visualized. At 12-13 weeks, its parameters are more than 3 mm.
3. The distance between the tubercles of the parietal region, or biparietal size (BDP). Normally, this indicator should be 17 mm at the 11th week; 20 mm at 12 weeks; 26 mm at the 13th week of pregnancy.
4. Embryo head circumference.
5. The distance from the forehead to the back of the head.
6. The structure of the brain, symmetry and size of its hemispheres, the quality of the closed skull.
7. Heart rate (HR). By means of this parameter, cardiac arrhythmia can be detected. When measuring the heart rate, the sonographer must be very careful: due to the short duration of pregnancy, it is possible to confuse the pulsation of the patient's vessels with the heartbeat of the embryo. Normally, the indicator in question varies between: 153-177 at the 11th week of pregnancy; 150-174 - at the 12th week; 147-171 - on the 13th.
8. Parameters of the heart and its arteries.
9. The structure of the femur, shoulder, tibia.
10. The distance between the inner and outer surface of the skin of the neck, or the thickness of the collar space (TVP). Normally, this indicator will be: at the 11th week of pregnancy 1.6-2.4 mm; at the 12th week - 1.6-2.5 mm; at the 13th week - 1.7-2.7 mm.
11. The structure of the chorion (placenta), its location. Upon detection of exfoliation of the chorion, its volumes are established and whether there is a tendency to progress. A similar phenomenon can provoke spotting and complaints of a pregnant woman about pain.
12. Shape and size of the yolk sac, the quality of supply of the umbilical cord with vessels. The yolk sac normally decreases in size by the 12th week of pregnancy, and at the time of ultrasound diagnosis, it should be a tiny (4-6 mm) cystic neoplasm of a rounded shape.
13. The structure of the uterus, its appendages. Particular attention is paid to the ovaries: for more later dates pregnancy, it is problematic to examine them.

At the time of the first screening ultrasound the fetus must be positioned correctly so that the specialist can carry out a qualitative inspection and make the necessary measurements.

If the child is not positioned correctly, the patient is asked to roll over from her back to her side, cough, or squat.

Double test (norms and interpretation)

For this type of examination, blood is used from a vein, which is taken on an empty stomach.

Biochemical screening is needed to determine the following parameters:

1.Protein Pregnancy (PAAP) -A )

This protein is produced by the placenta and increases with the course of pregnancy.

Normally, the indicators of this protein will be as follows:

• 11-12 weeks: 0.77-4.76 honey / ml.
• 12-13 weeks: 1.04-6.01 mU / ml.
• 13-14 weeks: 1.48-8.54 mU / ml.

A reduced amount of PAAP-A may be due to the following deviations:

1. There is a threat of miscarriage.
2. The developing embryo has Down syndrome, Edwards syndrome, or another genetic disease.

An increase in the level of PAAP-P in the blood of a future mother often does not have an important diagnostic value.

2. Amounts of human chorionic gonadotropin (hCG)

This hormone is produced in the first weeks of pregnancy, reaching a maximum level at the 12th week of pregnancy, after which the amount of the hormone in question decreases.

By studying the indicators of the amount of hCG in the blood of a pregnant woman, it is possible to determine the presence / absence of chromosomal abnormalities.

In the conclusion sheet, this parameter is written in the column “free β-hCG”.

In the first trimester of pregnancy, the norm of this hormone is as follows:

• 11th week: 17.3-130.2 ng / ml.
• 12th week: 13.3-128.4 ng / ml.
• 13th week: 14.3-114.7 ng / ml.

Elevated levels of hCG may indicate several phenomena:

• A developing fetus has Down syndrome.
• The mother-to-be has diabetes.
• The pregnant woman suffers from severe toxicosis.

A decrease in the level of the hormone in question may occur against the background of the following factors:

• There is a risk of miscarriage.
• Pregnancy formed outside the uterine cavity
• Failure of the placenta to perform its basic functions.
• The fetus has Edwards syndrome.

What pathologies can be detected on the screening of the first trimester?

In the first three months of pregnancy, through examinations, it is possible to identify or suspect the presence of the following ailments:

• Errors in the structure of the neural tube (meningocele).
• Down Syndrome. The prevalence of this disease: 1:700. Timely detection of this pathology made it possible to reduce the birth rate of sick babies (1 per 1100 cases).
• Umbilical hernia (omphalocele). An ultrasound study shows that internal organs are located in the hernial sac, and not in the abdominal cavity.
• Edwards syndrome (1:7000). It is characterized by a reduced heart rate, omphalocele, insufficient number of blood vessels on the umbilical cord, absence (inability to visualize) the nasal bone. Pregnant women over 35 years of age are at risk.
• triploidy. With this pathology, instead of 46, there are 69 chromosomes in a fertilized egg. Such a phenomenon may occur due to an incorrect structure of the egg, or when two spermatozoa penetrate one egg. Often, with such anomalies, women do not bear a fetus, or give birth to dead children. In those rare cases when it was possible to give birth to a live baby, the period of his life is limited to a few days / weeks.
• Patau disease (1:10000). Ultrasound ascertains retardation in the structure of the brain, tubular bones, increased heart rate, omphalocele. Often, babies that are born with a similar diagnosis live a maximum of a couple of months.
• Smith-Lemli-Opitz syndrome (1:30000). It is the result of genetic disorders, due to which the qualitative assimilation of cholesterol is impossible. The pathology under consideration is capable of provoking many malformations in development, the most serious of which are errors in the functioning of the brain and internal organs.

To confirm some of the above pathologies, it is required additional diagnostic measures, and in most cases they are invasive.

What can affect the results, and can the doctor make a mistake at the first screening?

Screening for the first trimester of pregnancy has certain disadvantages.

On the other hand, it is still necessary to conduct an examination: timely detection of a particular pathology will make it possible to terminate the pregnancy (if the fetus is with severe abnormalities), or take measures to maintain the pregnancy (if there is a threat).

In any case, it will be useful for any expectant mother to know that false positive screening results can occur in the following situations:

1. ECO. With artificial insemination, the parameters of the occipital part of the embryo will be 10-15% higher than normal. A double test will show an increased amount of hCG, and low level(up to 20%) RAAR-A.
2. Weight of the expectant mother: severe thinness is a consequence of a decrease in the amount of hormones, and with obesity, the opposite phenomenon is observed.

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. World Organization Health (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 this period pregnancy. The norm of MoM 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. At normal flow pregnancy, the amount of free estriol is constantly increasing.

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

Perinatal fetal screening is a set of diagnostic procedures performed at certain stages of pregnancy. 1st trimester screening allows you to identify possible anomalies and indirect signs of the presence of pathologies in the fetus in the early stages. This study, conducted from 11 to 14 weeks of pregnancy, includes ultrasound screening and biochemical research. Respectively, 1st trimester screening transcript occurs by comparing the results of the above diagnostic measures.

Deciphering ultrasound screening

An ultrasound examination of the 1st trimester, which is mandatory for every pregnant woman, allows you to identify signs of Down syndrome and some other pathologies in the development of the fetus. Screening of the 1st trimester, the interpretation of the results of which begins precisely with the interpretation of ultrasound data, should be carried out up to 14 weeks. After this period, some indicators may already be uninformative. The screening norms of the 1st trimester, the decoding of these norms largely depend on the period of fetal development.

One of the most important indicators that are a marker of chromosomal diseases and allow to identify an increased risk of Down syndrome in the 1st trimester is TVP - the thickness of the collar space.

Norms of ultrasound TVP:

at 10 weeks of pregnancy, the thickness of the fold is normal - 1.5-2.2mm;
normal at 11 weeks 1.6-2.4mm;
indicator 12 weeks - 1.6-2.5mm:
norm 13 weeks - up to 2.7 mm.

If the thickness of the collar fold exceeds the norm, this is a direct indication for further diagnosis.

The next indicator that is measured on ultrasound in the 1st trimester is KTP, that is, the coccygeal-parietal size. KTR should normally correspond to the following results:

10 weeks - 33-49 mm;
11 weeks - 42-58 mm;
12 weeks - 51-73 mm.

Deciphering ultrasound screening of the 1st trimester necessarily includes an assessment of another important indicator - the nasal bone. This marker, along with TVP, suggests that the child has Down syndrome. The nasal bone at 10-11 weeks should be detected, but at this time its dimensions are not yet estimated. At 12-13 weeks, the nasal bone should normally be at least 3 mm according to the results of ultrasound. During ultrasound diagnostics, the doctor also measures the heart rate, which should decrease slightly with the development of the fetus. So, if at 10 weeks the norm is 161-179 beats / minute, then at 13 weeks it is already 147-171 beats / minute.

The first screening ultrasound, performed in the 1st trimester, also evaluates biparietal size (BPD). This indicator, depending on the period, should be:

at 10 weeks pregnant - approx. 14 mm;
at 11 weeks approx. 17 mm;
at 12 weeks - approx. 20 mm;
at 13 weeks - 26 mm.

Having deciphered the results of the first demonstrative ultrasound, the doctor makes a conclusion about the presence (absence) of markers of various pathologies, and also determines what period at the time of the study corresponds to the development of the baby.

Deciphering biochemical screening

Biochemical research in the first trimester ("double test") is carried out in order to identify the risk of chromosomal abnormalities, namely Edwards and Down syndromes.

This screening involves the determination in the blood of a pregnant woman of specific markers that indicate the presence of certain pathologies in the child. These biochemical blood tests do not accurately diagnose chromosomal abnormalities in the fetus, however, deviations from the norm can reveal an increased risk of pathology.

Biochemical screening of the 1st trimester includes two studies:

determination of the presence in the blood of a pregnant woman of chorionic gonadotropin (β-hCG)

plasma protein A (PAPP-A) study

The norm of the free β-subunit of the hCG hormone in the first trimester is either 0.5–2 MoM, or (if measured in ng / ml) varies from 25.8 to 181.6 ng / ml at 10 weeks and gradually decreases by week 14 to 14, 2 - 114.7 ng / ml.

When biochemical perinatal screening of the 1st trimester is carried out, the interpretation of the results of β-hCG occurs as follows. If this marker is higher than normal, the child is diagnosed with an increased risk of Down syndrome. And, conversely, if the indicator is below the norm, there is reason to assume the presence of Edwards syndrome.

The second important indicator of PAPP-A, studied in the screening of the first trimester, may also indicate diseases of the unborn baby.

If the screening transcript found that PAPP-A is not normal, then the unborn child may also have Down syndrome or Edwards syndrome.

Once again, it should be noted that the likelihood of various pathologies in the development of the fetus should be assessed by the doctor on the basis of all the studies carried out in the complex. Deviation from the norm of only one indicator is not always an alarming signal. So, if the PAPP-A indicator is higher than the required standards, but the other indicators of the screening performed do not have deviations, then the risk of chromosomal diseases in the unborn baby is not high.

Risk calculation

To calculate the risks of pathological abnormalities in the 1st trimester, the results of all studies conducted during the screening process, including the results of ultrasound, are required. The calculation is carried out using a special computer program that takes into account not only the results obtained, but also the age and individual characteristics pregnant. The program gives the most accurate result, since it takes into account many factors in a complex way.

For a correct calculation of the risk of fetal anomalies, it is necessary that biochemical analyzes be taken in the same laboratory that performs computer calculation of the result. This is due to the peculiarities of the program, tuned to the individual standards and parameters of each laboratory.

The result of the computer risk calculation is written as a fraction, for example, 1:10, 1:300, 1:1000 or another ratio. This fraction shows the degree of risk of having a child with a pathology. Yes, the risk 1:200 means that at these screening rates, out of 200 children, 1 child has Down syndrome.

Further, on the basis of the received fraction, the final conclusion is made. If the test is positive, this indicates a high risk of anomalies and the need for additional research. A negative test, on the other hand, indicates a low risk.

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