In what week is screening done during the 1st trimester to get as much information about the child as possible?

Expectant mothers in vain rush to go for examination as soon as they find out about their interesting situation. The first screening, consisting of a blood test and ultrasound, is pointless to undergo early.

But you can’t postpone it either, because this mandatory procedure evaluates the processes of intrauterine development.

In the first three months of pregnancy, it is necessary to undergo screening in order to detect serious pathologies without delay.

These include an anomaly of the rudiment of the future nervous system, Patau syndrome, hernia of the umbilical cord (the intestines and liver are located outside the abdominal cavity - in the hernial sac), trisomy 21 (Down syndrome) or chromosome 18 (Edwards syndrome).

During the 1st trimester, ultrasound measures the growth of the embryo, determining its coccygeal-parietal size, circumference and biparietal size of the head.

At the first screening, you can see whether the right and left hemispheres are symmetrical relative to each other. At this time, the doctor will be able to see what structures have appeared in the brain.

The first screening involves measuring the length of the four main bones: the femur, tibia, upper arm and forearm.

The doctor checks where the internal organs (heart and stomach) are located, determines the size of the heart muscle and the veins and arteries leading from it.

Also, ultrasound in the first three months of pregnancy measures the abdominal circumference of the embryo.

Biochemical screening is aimed at determining plasma protein A and human chorionic gonadotropin.

Thanks to this study, the doctor learns about the presence of chromosomal abnormalities, possible risks and complications of pregnancy.

In the first trimester, the study should never be skipped by women who are married to a close relative or those who have had several miscarriages.

The first screening is a very important procedure for women who have had a viral or bacterial infection.

Women who have:

• previously had a frozen pregnancy;
• have relatives with genetic disorders;
• a child has already been born with Down or Edwards syndrome;
• age has reached 35 years;
• There was medical therapy with drugs prohibited during pregnancy.

In any case, you should not forget about visiting an ultrasound doctor, because every parent needs to make sure that their child is healthy.

Time frames and features

The expectant mother can go for an ultrasound of the fetus and donate blood for analysis at the 10th week of pregnancy. But doctors urge you to do this a little later - between 11 and 13 weeks.

It is at this time that it is possible to perform accurate measurements of the level of hormones and the collar zone of the fetus.

The deadline for examining the internal organs and limbs of the child at the 1st screening is the 14th week of pregnancy.

It is better to come for an ultrasound at least at this stage than even later, because doctors need to determine in time the time of birth and the degree of development of the child by its coccygeal-parietal size.

The first examination for the expectant mother will begin with an ultrasound. There is no need to prepare for a transvaginal examination, but for a transabdominal ultrasound you will have to drink a large amount of water (1 liter).

Filling the bladder before examination at 10–14 weeks is a must, otherwise the ultrasound will not pass through the abdominal wall.

Transabdominal ultrasound is performed through the abdominal wall. The woman needs to lie down for a while, exposing her stomach and groin area.

The doctor will move a special sensor treated with gel over the skin to improve glide.

To conduct a transvaginal examination at 10–14 weeks of pregnancy, a woman must completely remove clothing below the waist, lie down and bend her legs.

The doctor will insert a thin sensor into the vagina, on which a special condom will be placed, and evaluate the development of the fetus in the uterus.

This will not cause pain, but you may experience some spotting after the procedure.

Next time, for the second screening, no preparation will be required, because the ultrasound will help penetrate the accumulated amniotic fluid.

You will always have to prepare for blood sampling to determine the ratio of hormones. For a few days before the test at 10-14 weeks, the pregnant woman must give up sweets, meat and fish.

Typically, blood is drawn from a vein in the morning. You should not have breakfast immediately before this. You can have your last meal 4 hours before the procedure.

Ultrasound indicators in the 1st trimester

After an ultrasound scan of the first trimester, a woman wants to understand the information written in the examination report.

After all, mothers themselves do not know how much the coccygeal-parietal and biparietal dimensions, the thickness of the collar space and the heart rate should be.

The thickness of the nuchal translucency (TN) at the 10th week of pregnancy is normally 1.5 - 2.2 mm. At weeks 11 and 12, this figure increases to at least 1.6 mm.

At the 13th week of the 1st trimester it is already 1.7 - 2.7 mm. If the TVP value is higher than the established norm, then the child may have genetic abnormalities.

To determine the BPR indicator, you need to know exactly how many days have passed since the day the child was conceived.

It is important to evaluate the thickness of the nuchal translucency during the first trimester, since then measurement of this indicator will not be available.

At 10-11 weeks, the nasal bone should be clearly visible on the ultrasound equipment screen. A little later, the doctor already has the opportunity to measure it. The normal size of the nasal bone is from 3 mm. This indicator is observed in almost 100% of embryos.

When the first screening is done, it is determined how many times per minute the baby's heart beats. At week 10, the embryonic organ should be making more than 161 beats per minute.

The limit is 179 hits. A week later, the baby's heart should beat less frequently, ranging from 153 to 177 beats per minute.

The normal rate for the 12th week is 150–174 beats/min, and for the 13th week it’s 147–171 beats/min.

An excessively rapid heartbeat of a child may indicate the presence of an abnormality of the 21st pair of chromosomes, that is, Down syndrome.

During the first screening, the doctor must determine the size of the maxillary bone in the embryo. If this indicator is less than normal, the child should be suspected of having a genetic disease - trisomy.

After the 11th week of pregnancy, it becomes possible to examine the fetal bladder. An enlarged organ is a clear sign that a child has Down syndrome.

Blood test results in 1st trimester

Biochemical screening in the first three months of pregnancy reveals how much hCG and PAPP-A are contained in the blood serum. But the most informative indicator than hCG is β-hCG.

The fact is that hCG levels can change not only due to a woman’s pregnancy. Sometimes its value can be affected by hormonal imbalances and the use of certain medications.

The level of β-hCG depends solely on the duration of a woman’s pregnancy. At week 10, its value should fluctuate between 25.8 and 181.6 ng/ml, at week 11 – between 17.4 and 130.4 ng/ml.

During the 12th week, this figure is normally 13.4 – 128.5 ng/ml. When the 13th week of pregnancy ends, the level of β-hCG can reach 14.2 – 114.7 ng/ml.

The β-hCG value may indicate not only the presence of abnormalities in the fetus’s genome, but also the abnormal course of pregnancy and the deterioration of the woman’s condition.

If biochemical screening shows that a woman has elevated hormone levels, this may indicate:

• multiple pregnancy;
• acute toxicosis;
• Down syndrome;
• diabetes mellitus;
• hydatidiform mole.

The reason may also be the use of certain medications and the presence of cancer in the pregnant woman.

Low β-hCG levels indicate other problems:

• Edwards syndrome in the fetus;
• pregnancy in the fallopian tube;
• frozen pregnancy;
• risk of spontaneous abortion.

During the 1st trimester, it is very important to determine the level of PAPP protein in a woman. It is produced by the placenta and grows gradually throughout pregnancy.

When PAPP-A levels are low, the doctor suspects chromosomal abnormalities in the fetus. The most common are Down and Edwards syndromes.

But, if the screening showed a very high level of PAPP-A, then the pregnancy is frozen or it may be terminated unexpectedly.

It is better to determine the level of PAPP-A before the 14th week. It is not advisable to do this later, since it will no longer be possible to identify Down syndrome based on the content of this protein.

In order to find out in time important data about the process of intrauterine development of the child, take into account all the risks and identify anomalies, it is necessary to do an ultrasound and blood test on time.

According to the rules, a woman must undergo all first trimester examinations between 10 and 14 weeks.

If the pregnancy proceeds without complications and the mother feels well, then she will be able to look at her baby for the first time during the first screening at approximately 12 weeks of pregnancy. We will talk about what a screening study is at this stage in this article.

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What it is?

There are three pregnancy screenings. The Ministry of Health recommended that the very first be carried out at a period of 11-13 weeks; the 12th week is considered optimal. Then screening tests are carried out in the second and third trimesters (16-24 weeks and 30-36 weeks).

The examination, which is carried out at the very beginning of the process of bearing a baby, includes Ultrasound, and biochemical blood test for the content of the hCG hormone and PAPP-A protein. Based on a number of characteristic markers that are detected in the ultrasound room, as well as on the concentration of hormones and proteins in the pregnant woman’s tests, a preliminary calculation is made of the risk of a given woman having a baby with incurable and fatal genetic pathologies.

This stage of prenatal diagnosis allows us to identify women who are most likely to give birth to a toddler with Down syndrome, Turner and Cornelia de Lange syndromes, Patau syndrome, Edwards syndrome, severe neural tube defects, as well as other developmental anomalies that do not leave the slightest chance of cure and a normal life.

Previously, screening was carried out only for pregnant women who were at risk - women who were already 35 years of age or older, who became pregnant from a blood relative, those who had previously given birth to children with genetic problems, or women who have relatives with hereditary diseases from your side or your husband's side. If the expectant mother took medications that are prohibited during early pregnancy, she was also prescribed a screening test.

Now this diagnosis is prescribed to all representatives of the fair sex in an “interesting situation” without exception. Of course, a woman can, for personal reasons, refuse screening, but doing this is not entirely reasonable, because the examination itself does not oblige anyone to anything.

It should be noted that Based on the results of screening during pregnancy at 12 weeks, no one will make any diagnoses. This is not the purpose of the screening study. A woman will only have to calculate her individual risks of giving birth to a sick baby, and whether they are healthy can be determined by other methods that will be recommended by an obstetrician and a geneticist if the risks turn out to be high.

The first screening is considered the most important and informative. It is carried out free of charge in a consultation at the place of residence, directions for a blood test and a coupon to the ultrasound room are issued by the doctor with whom the woman is registered for pregnancy.

Procedure and preparation

When undergoing a perinatal examination in the first trimester, it is very important to follow a strict procedure. Ultrasound diagnostics and blood donation from a vein are planned for one day so that the time interval between these two actions is minimal.

Usually, they first undergo an examination in the ultrasound room, and then, with a completed form, go to the treatment room to donate blood. However, in some consultations the order is reversed. In any case, both examinations are completed strictly in one day.

To ensure that the test results are not influenced by negative factors, which include biochemical changes in the blood, accumulation of gases in the intestines, it is recommended that Prepare thoroughly for diagnosis. For two days you should go on a short diet - do not eat fatty and very sweet foods, fried and smoked foods, and six hours before the blood test you should not eat at all. A blood test is taken on an empty stomach.

Before the ultrasound, you should take Smecta or Espumisan a couple of hours to get rid of intestinal gases, which are faithful companions of pregnancy, since they can put pressure on the pelvic organs and the ultrasound results may be inaccurate.

Ultrasound at 12 weeks is performed with a transvaginal sensor; the second method is through the abdomen, until it gives a clear picture and idea of ​​what is happening inside the uterus.

On the appointed day, the woman comes to her obstetrician-gynecologist's office, is weighed, has her height measured and fills out a detailed questionnaire. The more data it contains, the more accurately the risks will be calculated. The questionnaire includes data on previous pregnancies, miscarriages, abortions, the woman’s age and weight, data on her bad habits (smoking, alcohol), information about her husband and the health status of close relatives.

Then there will be an ultrasound, and then blood donation. The general results will be entered into a single form; a special program will “compare” the genetic portrait of the pregnant woman along with her tests with the “portraits” of women with a high risk of giving birth to a sick baby. As a result, an individual calculation will be issued.

Ultrasonography

In the ultrasound room, the doctor will examine the baby, determine whether everything is fine with him, where he is located in the uterine cavity, and also check the baby for the presence of markers that indicate a high probability of having a child with genetic syndromes. At week 12, the expectant mother will be able to see her baby, listen to his little heart beat, and also see the movements of the fetus, which she does not yet physically feel.

The doctor will definitely indicate in the protocol for the first trimester screening study: how many fetuses are visualized in the uterine cavity, Do they show signs of vital activity? They will also describe the main dimensions, which will make it possible to clarify the timing of the “interesting situation” and find out how the baby’s development proceeds.

The normal development indicators at 12 weeks are as follows:

Fetal head circumference (HC) is 58-84 mm, most often 71 mm.

The coccygeal-parietal size (CPR) is 51-59 mm, most often 55 mm.

Bipariental head size (BPR) is 18-24 mm, most often 21 mm.

Heart rate (HR) – 140-170 beats per minute.

Motor activity is present.

In addition, the doctor determines the two most important markers for diagnosing genetic pathologies - the thickness of the collar space and the presence of nasal bones in the baby. The fact is that in children with severe developmental defects, the cervical fold is enlarged due to subcutaneous fluid (edema), and the nose is flattened. He will be able to examine the remaining facial bones only after one and a half to two calendar months.

TVP (thickness of the nuchal translucency) at 12 weeks in the absence of pathologies does not go beyond the range of 0.7-2.5 mm. If the baby exceeds this parameter slightly, the expectant mother may be advised to undergo an ultrasound again in a week. If TVP significantly exceeds the upper limits of normal, additional examination will be required; the risks of giving birth to a sick baby increase. We are talking about an excess of 3.0 mm and above.

Nasal bones can be much more difficult to discern; they are not always visualized at 12 weeks; the fetus may have its back to the doctor’s sensor and stubbornly refuse to turn around and let its nose be measured. If this was possible, normal values ​​for the length of the nasal bones at this stage are considered to be values ​​that do not fall within the range of 2.0-4.2 mm.

If the doctor indicated that at 12 weeks these bones are not visualized or their size is less than 2 mm, a program that calculates risks will increase the individual likelihood of giving birth to a child with Down, Turner, Patau syndrome.

In fact, the baby may just have a small, miniature nose, which is still difficult to capture in numerical value, especially on an old ultrasound scanner with low image clarity.

Theoretically, at 12 weeks you can already try to determine the sex of the child, because the external genitalia are formed, and if the baby is conveniently located and open to the eye of the diagnostician, they may well be noticed. However, you should not expect guarantees from the doctor that the birth will be a boy or a girl. The gender at this time can only be named tentatively (the probability of an accurate hit is approximately 75-80%). The doctor will more accurately assess the baby’s sexual characteristics at the next ultrasound, after 16-17 weeks of pregnancy.

Additionally, an ultrasound scan at the end of the first trimester evaluates the probable threats of miscarriage - thickened uterine walls may indicate the presence of hypertonicity, as well as the condition of the cervix, fallopian tubes, and cervical canal.

Blood chemistry

In an analysis of the venous blood of a pregnant woman, a laboratory technician identifies the amount of hCG hormone and plasma protein PAPP-A contained in it. Because only two blood components are assessed, the first screening test is called a "double test." The results of this study, in contrast to ultrasound data, which a woman is given immediately after undergoing it, will have to wait from several days to several weeks - this depends on how long the queue is lined up for the study in an accredited medical genetic laboratory.

One can only guess what numbers will be as a result of the analyzes, since individual laboratories use their own standards in calculations. To simplify decoding, it is customary to talk about the norm of PAPP-A and hCG in MoM - a value that is a multiple of the median. During a healthy pregnancy, when both the baby and the mother are doing well, both values ​​“fit” within the range of 0.5 to 2.0 MoM.

Fluctuations from this range up or down give rise to a lot of anxiety in pregnant women and There are many possible reasons:

Increased hCG.“Too much” in this indicator can be a sign of Down syndrome in a baby, as well as a sign that a woman is carrying more than one child. 2 fruits together give a practical double increase in the hormone norm. Elevated hCG may occur in a woman who suffers from excess weight, edema, toxicosis, diabetes and hypertension.

Decreased hCG. An insufficient level of this hormone, which is unique to pregnant women, is characteristic of the development of Edwards syndrome, and can also indicate the likelihood of a miscarriage or a delay in the development of the baby.

Decrease in PAPP-A. A decrease in plasma protein in a sample sometimes indicates the development of conditions such as Down, Patau, Edwards, and Turner syndromes. Also, an insufficient amount of this substance often indicates the baby’s malnutrition, which means that the baby is deficient in the nutrients and vitamins it needs for normal development.

Increase of PAPP-A. An increase in protein in a sample does not have much diagnostic value in terms of calculating the possible risk of chromosomal disorders. This indicator may be higher than normal in case of twins or triplets, as well as with a tendency to a large fetus.

How are risks calculated?

The results of tests and ultrasound, as well as all available information about the state of health of the pregnant woman and her age, are loaded into a special program. Thus, the calculation of individual risk is carried out by a machine, but the result is double-checked by a person - a geneticist.

Based on a combination of factors, individual the risk may look like a ratio of 1:450 or 1:1300 for each disease. In Russia, the risk is considered high: 1: 100. The threshold risk is 1: 101 – 1: 350. Thus, if a pregnant woman is calculated to have a probability of having a baby with Down syndrome of 1: 850, this means that one in 850 children is born to women with identical health indicators , age and other criteria will be born sick. The remaining 849 will be born healthy. It's low risk and nothing to worry about.

Women for whom screening diagnostics at 12 weeks show a high risk for a particular genetic disease are recommended to undergo additional diagnostics, since screening itself cannot be considered the basis for making a final verdict, it's not that accurate. You can take a non-invasive DNA test. Such an analysis costs several tens of thousands of rubles and is performed exclusively in medical genetic centers and clinics.

If the analysis confirms suspicions, you will still have to go for an invasive test.

Amniocentesis or chorionic villus biopsy can be offered immediately, without wasting time and money on examining the baby’s blood cells isolated from the mother’s blood, as is done with a non-invasive DNA test. However, both biopsy and amniocentesis involve penetration into the membranes to collect material for analysis. The procedure is carried out under ultrasound control only by experienced doctors, but the risk of fetal infection, rupture of water, and termination of pregnancy still remains.

Agreeing or not agreeing to undergo an invasive examination with high risks is a personal matter for every woman; no one can force her to do this. Analysis accuracy is 99.9%. If the disappointing assumptions are confirmed, the woman is given a referral to terminate the pregnancy for medical reasons. Whether to interrupt it or not should also be decided only by the woman herself and her family.

The waiting period for a baby is a magical time for every woman. And nothing can overshadow it, not even all kinds of examinations and tests that every pregnant woman has to do. However, some laboratory tests are somewhat frightening to expectant mothers, for example, screening.

What kind of procedure is this? Why and how is it done to pregnant women? Is she sick or not? At what stage and is it necessary to undergo screening during pregnancy? We will answer all these and many other questions in our publication today.

Biochemical, genetic, prenatal screening during pregnancy: what is it?

A pregnant woman learns about what screening is already in the first weeks of pregnancy. The local doctor is obliged to explain in detail the purpose of this study. However, if after visiting the doctor the expectant mother still has some questions, then here she can find the necessary answers.

During the entire period of bearing a child, the expectant mother must undergo the following screenings:

1. Ultrasonic.
2. Biochemical and genetic.

Let's consider each of the procedures in detail.

Biochemical screening during pregnancy has been practiced for more than a decade. The purpose of this examination is to detect the likelihood of deviations in the genetic development of the fetus. The most common diseases associated with such disorders are Down syndrome, pathologies of neural tube formation, and Edwards syndrome. Biochemical and genetic screening are a series of blood tests, during which the level of marker compounds is determined - human chorionic gonadotropin, alpha-fetoprotein, free estriol and others. The concentration of these substances in the mother’s blood changes depending on the condition of the fetus and the duration of pregnancy, which actually makes it possible to identify possible deviations.

Ultrasound screening of pregnant women is the first, but this procedure is repeated in each trimester. The main task of ultrasound is to identify possible numerous anomalies and anatomical defects in fetal development. At the 12th week of pregnancy, during screening, the thickness of the nuchal space and the coccygeal-parietal size are measured. In the middle of the second trimester, the fetus increases in size, which makes it possible to obtain more accurate information about it. At this stage of waiting for the baby, ultrasound screening allows us to identify the presence or absence of any pathologies in the unborn baby and his mother. Also, using a screening ultrasound, you can determine the gender of the child.

Prenatal screening (literally from Latin “prenatal screening”) includes a set of medical studies (ultrasound and laboratory) aimed at identifying risk groups for the development of fetal defects during pregnancy. It is considered one of the simplest, safest and most informative diagnostic methods for expectant mothers. Screening examinations are those examinations that are carried out en masse, that is, for all pregnant women without exception.

How is screening performed during pregnancy?

As mentioned above, there are different types of examinations during pregnancy. There are mandatory procedures, and there are also those that are carried out “as necessary.” Therefore, how screening is carried out depends on what type of study was prescribed for the expectant mother.

Biochemical and genetic analysis involves taking blood from a vein. Ultrasound screening is no different from the ultrasound procedure. That is, these studies do not cause any painful sensations. Next, we will describe in detail all the screening procedures that are performed on every woman during the prenatal period.

First, second, third screening during pregnancy: timing

Screening of a pregnant woman, the timing of which is always determined by the doctor, is mandatory in the first and second trimesters. In the third trimester, any laboratory tests are done rather out of necessity. However, if desired, a woman can do the screening she needs on her own, without a doctor’s prescription.

In the first trimester, an ultrasound examination is performed to measure the thickness of the nuchal translucency, as well as a biochemical blood test to determine or exclude suspected chromosomal abnormalities. A woman undergoes such procedures at the 11th week of the prenatal period.

Objectives:

• determining the duration of pregnancy;
• exclusion of gross malformations of the fetus (umbilical hernia, absence of the brain, etc.);
• conducting a “double test”: measuring hormonal levels of hCG and PAPP-A, pregnancy-related plasma protein A.

The second screening is carried out at 14-18, 20-22 weeks of pregnancy. It combines a “triple” or “quadruple” test, ultrasound, and Doppler study of blood flow. The purpose of these studies is:

• determining the condition of the cervix and excluding symptoms of miscarriage;
• study of the anatomical structures of the fetus in order to prevent the slightest deviations from normal development;
• assessment of the condition of the placenta and umbilical cord using Doppler imaging;
• blood test for AFP, hCG, free estriol and inhibin A to diagnose fetal malformations.

The third screening is carried out at 31-33 weeks of pregnancy with mandatory ultrasound, as well as CTG (cardiotocography) of the fetus and Doppler study of blood flow.

Objectives:

• determination of the presenting part of the fetus in order to select further labor tactics;
• diagnosis of possible fetal development delay;
• conducting a functional assessment of the condition of the unborn child using CTG and Dopplerography (ultrasound);
• determination of the amount of amniotic fluid, location and degree of maturity of the placenta.

All of these procedures are ultrasound and laboratory tests. There is an opinion that an ultrasound at 12-13 weeks is performed transvaginally, as when determining the presence of pregnancy at 5-6 weeks. But this is not the case, since screening ultrasound is performed exclusively in a standard way, namely by passing a special sensor over the woman’s abdomen.

Explanation of screening: norm, indicators

According to the blood test, quantitative indicators for all tested substances are determined. Conditional norms for each stage of pregnancy have been derived.

One of the most important indicators of the first screening, which is a marker of chromosomal diseases and makes it possible to identify an increased risk of Down syndrome in the 1st trimester, is TVP - the thickness of the nuchal translucency.

Ultrasound standards for TVP in the first trimester:

• at 10 weeks of pregnancy, the normal thickness of the fold is 1.5-2.2 mm;
• at 11 weeks the norm is -1.6-2.4 mm;
• indicator at 12 weeks - 1.6-2.5 mm;
• the norm at 13 weeks is 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 CTE, that is, the coccygeal-parietal size. CTE should normally correspond to the following results:

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

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

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

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

Screening standards for the 2nd trimester are as follows:

• 16 weeks - 10,000-58,000 mU/ml;
• 17-18 weeks - 8,000-57,000 mU/ml;
• 19 weeks - 7,000-49,000 mU/ml.

• 12-14 weeks - 15-60 U/ml;
• 15-19 weeks - 15-95 U/ml;
• 20-24 weeks - 27-125 U/ml.

• 13-14 weeks - 5.7-15 nmol/l;
• 15-16 weeks - 5.4-21 nmol/l;
• 17-18 weeks - 6.6-25 nmol/l;
• 19-20 weeks -17.5-28 nmol/l;
• 21-22 weeks - 12-41 nmol/l.

In addition to this data, the average MoM coefficient is displayed - the ratio of indicators. Normally, it fluctuates between 0.5-2.0.

A decreased AFP in test results may indicate Down and Edwards syndrome, fetal death, or incorrect determination of the gestational age; increased - about malformations of the nervous system in a child, umbilical hernia, pathologies of the anterior abdominal wall, Meckel's syndrome, esophageal atresia, liver necrosis.

Reduced estriol is detected in Down syndrome, fetoplacental insufficiency, high risk of premature birth, intrauterine infection, fetal anencephaly, adrenal hypoplasia. An increased level of estriol indicates a multiple pregnancy, a large fetus, diseases of the urinary system or liver in the expectant mother.

Ultrasound screening standards for the third trimester:

1. Thickness of the placenta: 25.3-41.6 mm - at 32 weeks, at 34 weeks - 26.8-43.8 mm.
2. Degree of placenta maturity: I-II.
3. Amniotic fluid index: 81-278 mm.
4. The cervix should not be shorter than 30 mm, and its cervix should be closed.
5. The tone of the uterus indicates that labor may occur soon.

The 3rd trimester screening standards for the fetus depend on the period (averages from 32 to 34 weeks are indicated):

1. Biparietal size: on average 85-89 mm.
2. Fronto-occipital size: about 102-107 mm.
3. Head circumference: 309-323 mm.
4. Abdominal girth: 266-285 mm.
5. Shin bones: 52-57 mm.
6. Thigh: 62-66 mm.
7. Forearm: 46-55 mm.
8. Shoulder: 55-59 mm.
9. Height: 43-47 cm.
10. Weight: 1790-2390 grams.

CTG 3 screening standards are 8-12 points.

Interpretation of 3rd trimester screening for hormones: they should all be within 0.5-2.5 MoM. The risk for all pathologies should not be more than 1:380 or “high risk” should not be written. Then this is the norm.

Prenatal screening for multiple pregnancies

At 12-13 weeks of the prenatal period, a geneticist determines the number of fetuses in the womb of the expectant mother. When a multiple pregnancy is detected, it is observed with increased monitoring. That is, diagnostics of the condition of the woman’s body and fetus is carried out more often.

First of all, this concerns ultrasound examination, since with this examination the doctor has the opportunity to clearly see the woman’s organs and fully observe the development of the babies. If any abnormalities appear in the fetus, the doctor will be able to identify them in a timely manner.

Screening during pregnancy: reviews

At various forums, the topic of ultrasound and laboratory tests under consideration is discussed quite often. Reviews about screening during pregnancy vary. Sometimes women refuse to undergo an ultrasound due to the fact that the harmful radiation from the device can have an adverse effect on the fetus. However, doctors say that ultrasound does not harm either the child or the mother. This is just a high-frequency sound, thanks to which the doctor can see the outlines of the organs and body of the fetus. Without an ultrasound, it is impossible to determine abnormalities in the development of pregnancy.

Other mothers refuse examinations for the reason that there are no close relatives with genetic disorders. However, there are always factors that negatively affect pregnancy. For example, the woman’s age, diabetes or other serious illnesses. Therefore, doctors insist on screening all pregnant women, without exception.

There are also particularly impressionable women who do not want to undergo the examinations in question because if they have bad results, they will be very worried and worried, and this can have a bad effect on the child. But experts remind that even if risks of pregnancy are identified, there are many procedures that can solve these problems.

Should pregnant women be screened: pros and cons

Unfortunately, sometimes it happens that a child already has some pathologies from the moment of conception. And screening is a study that allows you to determine the presence of pathological changes in the fetus and help the expectant mother. Answering the question whether screening is mandatory during pregnancy, I would like to note that the choice is always yours. Of course, your local doctor will recommend these procedures, but no one has the right to force them on you.

The positive aspects of screening examinations are that they themselves are necessary and useful. The negative point is that the tests are expensive. Therefore, if the family budget does not allow such spending, then you can do without it.

Screening is mandatory if you are 35 years or older. The child's father is over 45 years old. If one of the parents or close relatives has hereditary diseases. Screening should also be done for women who have had two or more spontaneous abortions or who already have a child in the family with congenital defects or chromosomal diseases. Doctors insist on undergoing such studies if one of the parents was exposed to radiation before the baby was conceived.

Especially for - Nadezhda Vitvitskaya

Modern methods of examination during pregnancy stipulate that the expectant mother should three times pass - once in each trimester. And although the term itself is a little scary with its unusual “frightening” medical name, there is nothing alarming or unusual about it. Screening is just a general comprehensive examination of the pregnant woman and the fetus in order to determine various indicators and identify possible abnormalities.

Preparing for screening

Carrying out the first screening during pregnancy requires careful preparation and compliance with a number of requirements and recommendations. During subsequent examinations and trimesters, the list of preparatory activities will become significantly smaller.

Before undergoing the first prenatal screening, a woman should do the following:

• during the day before the examination, refrain from consuming potential products (citrus fruits, seafood, etc.);
• refrain from fried and fatty foods;
• on the morning before the examination, refrain from breakfast until blood is taken for analysis;
• in preparation for abdominal passage (through the stomach), fill the bladder with liquid by drinking 0.5 liters of still water half an hour before the examination.

information In addition, it is advisable to perform normal hygiene procedures, while excluding the use of scented cosmetics or hygiene products.

Standard values

When passing the first screening, special pay attention on following indicators And their compliance recommended standard values.

1st trimester screening is included in the general set of examinations during the gestation period to assess the child’s health and possible threats to pregnancy. Screenings are a common research method that applies not only to pregnant women: referrals for screening studies are also prescribed for newborns, as well as any population groups included in the risk group for developing any diseases, abnormalities, or dysfunctions.

Screening studies allow you to determine the likely possibility of pathology. In the first trimester of pregnancy, screening combines ultrasound examination and analysis of blood parameters, while interpretation of the results is carried out exclusively in a comprehensive analysis of both types of research.

First screening during pregnancy: period and timing of the study

During pregnancy, women are asked to undergo three screenings to identify and promptly correct possible deviations in the course of pregnancy or fetal development.

1 screening is carried out in the first trimester. The timing of pregnancy in the classic version is established on the basis of obstetric calculation, where the first day of the gestational period is considered the date of the beginning of the last menstruation before the onset of pregnancy. With the calendar method of determining the duration of pregnancy, experts start from the day of conception. However, since during physiological conception it is difficult to determine this date (the day of ovulation and the day of fusion of the egg and sperm may differ by 3-5 days), it is recommended to adhere to the obstetric technique, focused on the date of the last menstruation.

With a long menstrual cycle, the specialist can make changes to the screening dates, however, on average, the first screening test is carried out between 11 and 14 weeks of gestation, limiting the upper limit of the period to 13 weeks and 6 days from the date of the start of the last menstrual bleeding.

Why was this particular period chosen for the first screening? At 12 obstetric weeks, the border between the embryonic and fetal or fetal periods of development passes: the unborn baby passes from the embryonic stage to the fetus. The presence of formed structures and changes in the body make it possible to assign a new status to the future baby at the perinatal stage of development.

Also, this period is the minimum during which it is possible to identify the most common, although quite rare, deviations, as well as the reactions of the mother’s body to the development of a new life.

Screening – voluntary or obligatory?

Since early diagnosis of possible abnormalities allows you to quickly and effectively help the expectant mother correct possible negative consequences, screening studies during gestation are strongly recommended for all pregnant women, regardless of age, health status and the presence of healthy children. Deviations recorded during the study can occur spontaneously without correlation with the health of parents, relatives and lifestyle.

Despite the fact that the screening study is carried out on the direction of a gynecologist, you can refuse screening. This procedure is voluntary, although it is recommended by the Ministry of Health as part of the medical support of pregnancy for any woman.

If you refuse screening for one reason or another, you must remember that this study is useful for everyone, and especially for some categories of expectant mothers. High-risk groups include:

• expectant mothers over the age of 35, regardless of previous experience of pregnancy and childbirth. This recommendation is associated with an increase in the number of possible chromosomal abnormalities during the onset of the aging process of the body;
• women who have been diagnosed with a condition that threatens spontaneous miscarriage or miscarriage, frozen, non-developing pregnancy;
• a history of infectious diseases (including influenza, ARVI during the first trimester);
• parents with genetic disorders, women who, during previous pregnancies, had a high risk of genetic abnormalities, the presence of pathologies, or have children born with chromosomal abnormalities;
• pregnant women forced to take medications that are restricted or prohibited for use during or immediately before gestation, certain types of vaccinations and medical procedures that briefly preceded pregnancy;
• women whose pregnancy resulted from a close relationship;
• women with bad habits: alcohol, drug addiction, etc.

A screening study does not pose a risk to the fetus or mother, so refusing diagnostics, which can reveal deviations that can be easily corrected at a given time, is at least unreasonable.

The study is carried out in public clinics free of charge. If you choose, you can undergo screening in any other clinic; if necessary, it is possible to repeat both the full study and one of its stages, if the timing of pregnancy allows.

What is included in the first perinatal screening?

Screening in the first trimester of pregnancy is limited to an ultrasound examination of the condition of the woman’s fetus and uterus, as well as a biochemical test of the pregnant woman’s blood, which determines the level of relevant hormones and the presence of certain markers.

The size of the fetus, the characteristics of the development of its body parts, bones, the presence of certain parts of the circulatory system in combination with the results of a blood test make it possible to confirm the correctness of the child’s development and the reaction of the mother’s body, or to suspect the possibility of some deviations.

How to prepare for the first screening?

Ultrasound examination of the fetus and uterus can be carried out using two methods: using a device with a transvaginal sensor or a transabdominal method of external examination through the surface of the peritoneum.

In the first case, preparation for the study consists of emptying the bladder immediately before the ultrasound; in the second, before the study it is necessary to fill the bladder, which will create the necessary darkening and contrast. The bladder should be filled approximately 30 minutes before the start of the study; the required volume of fluid is from 0.5 to 0.7 liters. It is preferable to drink non-carbonated drinking water and not visit the toilet, starting from 4 hours before the time of visiting a specialist until the end of the ultrasound.

During the procedure itself, the position of the fetus is an important factor. If the child lies in such a way that it is difficult to calculate the exact dimensions of some parts of the body, then the expectant mother may be asked to walk, bend over, tense and relax her stomach, imitate a cough, etc. At this time, it is sometimes possible to determine the sex of the unborn child, but for For a more accurate result, it is better to wait for the second ultrasound at a period above 20 weeks.

Blood biochemistry during screening of the first trimester should be carried out strictly after an ultrasound examination. The blood formula in the mother's body changes daily during pregnancy, and without correlation with the ultrasound date, a specialist will not be able to correctly interpret the analysis data.

For the most reliable results of a biochemical blood test, it is necessary to exclude all factors that may affect the functioning of various organs. Thus, preparation for the second stage of screening includes:

• exclusion from the diet of foods that are potential allergens for all women (cocoa products, nuts, shellfish, citrus fruits, out-of-season vegetables and fruits) and identified allergens for pregnant women with a history of allergic reactions. It is necessary to notify a specialist about the presence of an allergy at the time of screening or shortly before it, this will allow a more accurate assessment of the test results. There is no need to talk about the need not to drink alcohol during pregnancy, but before screening this rule is especially important and applies even to small doses of alcohol on holidays;
• The last meal should be 12 hours before blood sampling for testing, in the evening of the previous day. After getting up and before the analysis, you should not drink;
• immediately before taking blood, you need to sit for 15-20 minutes, avoid stress and physical activity (jogging after the bus, climbing long stairs, etc.).

Failure to comply with the above rules may lead to distortions in test results, which may be incorrectly interpreted as a deviation in the development of the fetus or the course of pregnancy. Such unnecessary risks must be avoided.

Fetal parameters assessed by ultrasound during first trimester screening

During the ultrasound examination, the specialist evaluates the size of the fetus according to various indicators, as well as some important parameters of the child’s body at this period of development, features of the development and condition of the placenta and the mother’s uterus.

In the ultrasound results during the first screening, you can see the following designations:

• KTR, or the length of the fetus from the crown to the tailbone: this is how the process of intrauterine development indicates the “growth” of the child, since the most characteristic position of the fetus - with legs bent and pulled to the chest, especially in the later stages - does not allow determining the length of the entire body. Full “height” can be roughly estimated based on the length of the femur bone, which, like the length of the shoulder and forearm bones, is an important indicator of fetal development;
• OG is an indicator of the size of the fetal head, measured by circumference (calculated based on diameter);
• BPR is an indicator of the bioparietal size of the head between the parietal bones. This indicator reflects both the development of the fetal head structures and, in later stages, allows us to make assumptions about the mother’s preferred method of delivery. With a large volume of the skull and a narrowed pelvis, a cesarean section will most likely be offered. The distance from the forehead to the back of the child’s head is also measured;
• TVP is an indicator of the thickness of the nuchal space or cervical fold of the fetus, assessed only in the first trimester. By week 16, this formation is transformed into new organs, and during the first screening for this indicator, in combination with blood markers, the absence or increased likelihood of the presence of chromosomal disorders is diagnosed;
• the thickness of the nasal bone as a probable indicator of the presence of genetic abnormalities is measured by ultrasound at 12-13 weeks; ultrasound at 11 obstetric weeks in most cases allows only to notice its presence and the beginning of its formation;
• structural features of the brain, skull bones: this indicator describes how symmetrically and in accordance with the norm the skull and brain tissue of the fetus develop;
• Heart rate, a measure of the heart rate or heartbeat, is assessed according to age-specific norms. Also, when examining the heart, if possible, the specialist examines the size and structural parts of the heart muscle. The location of the heart, stomach, large arteries and veins is also examined;
• localization of the chorion (placenta), thickness of this organ. Later studies will also examine the presence and quantity of calcifications - inclusions indicating physiological aging of the placenta;
• number of umbilical vessels;
• volume and condition of amniotic fluid;
• characteristics of the tone of the uterus and cervical pharynx.

Average values ​​of basic parameters according to weeks of pregnancy:

Interpretation of the results of biochemical screening of the first trimester

The main indicators that specialists focus on when deciphering the results of a biochemical blood test at this stage are the level of human chorionic gonadotropin, the pregnancy marker hormone hCG, and plasma protein A, or PAPP-A.

The fetal membrane (chorion), which begins to form immediately after fertilization of the egg by the sperm, produces human chorionic gonadotropin on the very first day. However, this hormone reaches reference values ​​for determining pregnancy no earlier than after 2 weeks. Highly sensitive rapid tests and blood tests for pregnancy determine the presence of this particular component.

In the first weeks of pregnancy, the level of human chorionic gonadotropin increases, doubling almost daily. The level of this hormone reaches its peak concentration at 11-12 weeks, then it decreases and stabilizes at insignificant levels.
High hCG in relation to the norm may indicate the following abnormalities and/or physiological conditions:

• multiple pregnancy, in which the hormone is produced by several chorions;
• maternal endocrinological diseases (diabetes mellitus) in history or developing during gestation;
• manifestation of severe toxicosis in the first trimester;
• chromosomal disorder - Down syndrome in the fetus.

A reduced level of human chorionic gonadotropin (hCG) relative to reference values ​​may indicate the following disorders:

• placental insufficiency;
• presence of ectopic pregnancy;
• increased risks of miscarriage and spontaneous abortion;
• genetic disorder - Edwards syndrome in the fetus.

When assessing PAPP-A levels, only decreased values ​​are significant. They may indicate a threat of miscarriage due to an inadequate response of the mother's immune system or poor functioning of the placenta, as well as some chromosomal abnormalities in the fetus.

Comprehensive interpretation of screening results

The first trimester screening results, after a full assessment of all indicators, will contain the following data:

• risks of deviations associated with maternal age;
• assessment and interpretation of maternal biochemical blood parameters;
• the likelihood of the presence or occurrence of various diseases;
• MoM value

Based on the results of an ultrasound examination and a biochemical blood test, specialists bring the data together and assign the so-called MoM index (multiple of median). This coefficient is formed on the basis of variable indicators characteristic of the range of research results of healthy women with a normal pregnancy and a timely developing fetus.

The norms for the first screening range from 0.5 to 2.5 units for a singleton pregnancy, and up to 3.5 if two or more babies are expected.
After calculating the IOM, the results are entered into a program that takes into account all factors that influence the health of the mother and child and the course of pregnancy: age, height-to-weight ratio, some diseases (in particular, diabetes), the presence of bad habits (tobacco smoking), number of pregnancy fetuses, physiological or extracorporeal method of conception, etc.

Based on the evaluation of all data, the program provides a probable risk of genetic abnormalities in the fetus. The result is presented as a proportion of 1:1000 for several genetic diseases, expressing the risk of occurrence of a given syndrome in each specific case. An index of 1:380 or more is considered a positive result of a low risk of violations; an index below 1:380 means an increase in risk.

But this indicator is not a final diagnosis, but an assessment of probabilities. So, if a specialist’s conclusion contains an index of 1:70 for Down syndrome, this means that only 1 out of 70 women with similar results gives birth to a child with developmental disorders. In 69 cases, pregnancy proceeds without abnormalities and ends in the birth of a healthy child.

The following factors influence the distortion of results:

• non-compliance with the rules of preparation for biochemical analysis;
• outdated ultrasound equipment;
• in vitro fertilization;
• endocrinological disorders (diabetes mellitus of both types);
• multiple pregnancy;
• increased maternal body mass index (overweight).

What to do if the screening results are disappointing?

Many women are afraid to undergo the “first exam” in the life of the fetus, fearing both hearing negative news and hasty prescriptions and even pressure to terminate the pregnancy. If you have any doubts about the results, you can undergo additional screening, following the rules of preparation and alternation of ultrasound and biochemistry, and evaluate the condition and results as a whole.

In fact, “high risk” is diagnosed at rates between 1:250 and 1:380 for any syndrome, which means a slightly increased, but not necessarily, likelihood of a child having genetic abnormalities. With such indicators, it is recommended to lead a healthy lifestyle, regularly see a gynecologist and undergo genetic counseling.

In some cases, a genetic specialist may suggest undergoing additional examination for an accurate diagnosis (chorionic villus biopsy, amniocentesis, cordocentesis), on the basis of which recommendations for parents will be made.