The Center for Immunology and Reproduction has been successfully working for many years prenatal screening program. Our specialists are invited to give lectures at specialized conferences and in other clinics. Our laboratory receives consistently good marks in the quality control system. Specially trained specialists carry out risk calculations.

What is prenatal diagnosis?

The word "prenatal" means "before birth." Therefore, the term “prenatal diagnosis” means any studies that make it possible to clarify the condition of the intrauterine fetus. Since human life begins at the moment of conception, various health problems can occur not only after birth, but also before birth. Problems can be different:

• fairly harmless, which the fetus can handle on its own,
• more serious when timely medical care will preserve the health and life of the intrauterine patient,
• severe enough that modern medicine cannot cope with.

To determine the health status of the intrauterine fetus, prenatal diagnostic methods are used, which include ultrasound, cardiotocography, various biochemical studies, etc. All these methods have different capabilities and limitations. Some methods are quite safe, such as ultrasound. Some carry some risk to the fetus, such as amniocentesis (sample of amniotic fluid) or chorionic villus sampling.

It is clear that prenatal diagnostic methods associated with the risk of pregnancy complications should be used only when there are compelling indications for their use. In order to narrow as much as possible the circle of patients in need of invasive (i.e., associated with intervention in the body) methods of prenatal diagnosis, the selection is used risk groups development of certain problems in the intrauterine fetus.

What are risk groups?

Risk groups are those groups of patients among whom the likelihood of detecting a particular pregnancy pathology is higher than in the entire population (among all women in a given region). There are risk groups for the development of miscarriage, gestosis (late toxicosis), various complications during childbirth, etc. If a woman, as a result of an examination, is found to be at risk for a particular pathology, this does not mean that this pathology will necessarily develop. This only means that this patient is more likely to develop one or another type of pathology than other women. Thus, the risk group is not identical to the diagnosis. A woman may be at risk, but there may not be any problems during pregnancy. And vice versa, a woman may not be at risk, but she may have a problem. The diagnosis means that this or that pathological condition has already been discovered in this patient.

Why are risk groups needed?

Knowing that the patient is in one or another risk group helps the doctor correctly plan the management of pregnancy and childbirth. Identification of risk groups makes it possible to protect patients who are not included in risk groups from unnecessary medical interventions, and vice versa, it allows us to justify the prescription of certain procedures or studies for patients included in risk groups.

What is screening?

The word screening means "sifting." In medicine, screening means conducting simple and safe studies on large groups of the population in order to identify groups at risk of developing a particular pathology. Prenatal screening refers to studies carried out on pregnant women to identify groups at risk of pregnancy complications. A special case of prenatal screening is screening to identify groups at risk of developing congenital defects in the fetus. Screening does not allow identifying all women who may have one or another problem, but it makes it possible to identify a relatively small group of patients, within which the majority of people with this type of pathology will be concentrated.

Why is screening for fetal defects necessary?

Some types of congenital defects in the fetus are quite common, for example, Down syndrome (trisomy 21 pair of chromosomes or trisomy 21) - in one case in 600 - 800 newborns. This disease, like some other congenital diseases, occurs at the time of conception or in the earliest stages of fetal development and can be diagnosed quite early in pregnancy using invasive prenatal diagnostic methods (chorionic villus sampling and amniocentesis). However, such methods are associated with the risk of a number of pregnancy complications: miscarriage, the development of a conflict regarding the Rh factor and blood group, infection of the fetus, the development of hearing loss in the child, etc. In particular, the risk of developing a miscarriage after such studies is 1:200. Therefore, these studies should be prescribed only to women at high risk. Risk groups include women over 35 and especially over 40, as well as patients who have given birth to children with developmental defects in the past. However, children with Down syndrome can be born to very young women. Screening methods - completely safe studies carried out at certain stages of pregnancy - make it possible with a very high degree of probability to identify groups of women at risk of Down syndrome who may be indicated for chorionic villus sampling or amniocentesis. Women who are not at risk do not need additional invasive examinations. Detection of an increased risk of developing fetal defects using screening methods is not a diagnosis. The diagnosis can be made or rejected with additional tests.

What types of birth defects are screened for?

• Down syndrome (trisomy of the twenty-first pair of chromosomes)
• Edwards syndrome (trisomy eighteenth pair)
• Neural tube defects (spina bifida and anencephaly)
• Smith-Lemli-Opitz syndrome
• Corneille de Lange syndrome

What types of tests are performed to screen for the risk of birth defects in the fetus?

By types of research highlight:

• Biochemical screening: blood test for various indicators
• Ultrasound screening: identifying signs of developmental abnormalities using ultrasound.
• Combined screening: a combination of biochemical and ultrasound screening.

The general trend in the development of prenatal screening is the desire to receive reliable information about the risk of developing certain disorders as early as possible in pregnancy. It turned out that combined screening at the end of the first trimester of pregnancy (10-13 weeks) makes it possible to approach the effectiveness of classical biochemical screening in the second trimester of pregnancy.

Ultrasound screening, used for mathematical processing of the risks of fetal abnormalities, is carried out only once: at the end of the first trimester of pregnancy.

Concerning biochemical screening, then the set of indicators will be different at different stages of pregnancy. During pregnancy 10-13 weeks the following indicators are checked:

• free β-subunit of human chorionic hormone (free β-hCG)
• PAPP-A (pregnancy associated plasma protein A), pregnancy-associated plasma protein A

A calculation of the risk of measuring fetal anomalies based on the measurement of these indicators is called double biochemical test in the first trimester of pregnancy.

Using a double test in the first trimester, the risk of detection in the fetus is calculated Down syndrome (T21) And Edwards syndrome (T18), trisomy on chromosome 13 (Patau syndrome), triploidy of maternal origin, Shereshevsky-Turner syndrome without dropsy. The risk of neural tube defects cannot be calculated using a double test, since the key indicator for determining this risk is α-fetoprotein, which begins to be determined only from the second trimester of pregnancy.

Special computer programs make it possible to calculate the combined risk of fetal developmental anomalies, taking into account biochemical indicators determined in a double test in the first trimester and the results of an ultrasound scan done at 10-13 weeks of pregnancy. This test is called combined with TVP double test in the first trimester of pregnancy or triple test in the first trimester of pregnancy. The risk calculations obtained using the combined dual test are much more accurate than risk calculations based on biochemical parameters alone or on ultrasound alone.

If test results in the first trimester indicate that the fetus is at risk for chromosomal abnormalities, the patient may be tested to exclude the diagnosis of chromosomal abnormalities. chorionic villus biopsy.

During pregnancy 14 - 20 weeks by last menstruation ( recommended time frame: 16-18 weeks) the following biochemical parameters are determined:

• α-fetoprotein (AFP)
• Inhibin A

Based on these indicators, the following risks are calculated:

• Down syndrome (trisomy 21)
• Edwards syndrome (trisomy 18)
• neural tube defects (spina bifida and anencephaly).
• Risk of trisomy 13 (Patau syndrome)
• Triploidy of maternal origin
• Shereshevsky-Turner syndrome without hydrops
• Smith-Lemli-Opitz syndrome
• Corneille de Lange syndrome

This test is called quadruple test in the second trimester of pregnancy or quadruple biochemical screening in the second trimester of pregnancy. A truncated version of the test is the so-called triple or double tests of the second trimester, which includes 2 or indicators: hCG or free β-hCG subunit, AFP, free estriol. It is clear that the accuracy of the second trimester double or double test is lower than the accuracy of the second trimester quadruple test.

Another option for biochemical prenatal screening is biochemical risk screening for neural tube defects only in the second trimester of pregnancy. In this case, only one biochemical marker is determined: α-fetoprotein

At what stage of pregnancy is second trimester screening performed?

At 14 - 20 weeks of pregnancy. The optimal period is 16 - 18 weeks of pregnancy.

What is the quadruple test in the second trimester of pregnancy?

The main option for biochemical screening of the second trimester in the Center is the so-called quadruple or quadruple test, when the determination of inhibin A is added to the determination of the three above indicators.

Ultrasound screening in the first trimester of pregnancy.

In the first trimester of pregnancy, the main measurement used in calculating risks is the width of the cervical translucency (English “nuchal translucency” (NT)”, French “clarté nuchale”). In Russian medical usage, this term is often translated as “neck space” (TVP) or “cervical fold”. Cervical transparency, nuchal space and cervical fold are complete synonyms that can be found in various medical texts and mean the same thing.

Cervical translucency - definition

• Cervical transparency is what the accumulation of subcutaneous fluid on the back of the fetal neck looks like during ultrasound examination in the first trimester of pregnancy.
• The term cervical translucency is used regardless of whether it is septated or whether it is limited to the cervical region or surrounds the entire fetus
• The frequency of chromosomal and other abnormalities is related primarily to the width of the transparency, and not to how it looks overall
• During the second trimester, the transparency usually resolves, but in some cases it can develop into either cervical edema or cystic hygromas with or without generalized edema.

Cervical translucency measurement

Gestation period and coccygeal-parietal size

The optimal period of pregnancy for measuring PB is from 11 weeks to 13 weeks 6 days. The minimum KTR size is 45 mm, the maximum is 84 mm.

There are two reasons for choosing 11 weeks as the earliest time to measure PN:

1. Screening requires the ability to perform chorionic villus sampling before the time when this study may be complicated by amputation of fetal limbs.
2. On the other hand, many gross fetal defects can be detected only after 11 weeks of pregnancy.

• A diagnosis of omphalocele is possible only after 12 weeks.
• Diagnosis of anencephaly is possible only after 11 weeks of pregnancy, since only from this period ultrasound signs of ossification of the fetal skull appear.
• Assessment of the four chambers of the heart and large vessels is possible only after 10 weeks of pregnancy.
• The bladder is visible in 50% of healthy fetuses at 10 weeks, in 80% at 11 weeks, and in all fetuses at 12 weeks.

Image and measurement

To measure SB, the ultrasonic device must have a high resolution with a video loop function and calibrators that can measure the size with an accuracy of tenths of a millimeter. PB can be measured using an abdominal probe in 95% of cases; in cases where this is not possible, a vaginal probe should be used.

When measuring HF, only the head and upper part of the fetal chest should be included in the picture. The magnification should be at its maximum, so that a slight shift of the markers results in a change in measurement of no more than 0.1 mm. When enlarging a picture, before or after capturing the image, it is important to reduce the gain. This avoids measurement errors when the marker falls into a blurred area and thus the size of the BL will be underestimated.

A good sagittal section should be obtained, the same quality as when measuring CTE. The measurement should be made in the neutral position of the fetal head: extension of the head can increase the TVP value by 0.6 mm, flexion of the head can decrease the value by 0.4 mm.

It is important not to confuse the fetal skin and the amnion, since at this stage of pregnancy both formations look like thin membranes. If in doubt, you should wait until the fetus moves and moves away from the amnion. An alternative method is to ask the pregnant woman to cough or lightly tap the pregnant woman's abdominal wall.

The greatest perpendicular distance between the internal contours of the cervical transparency is measured (see figure below). Measurements are taken three times, the largest size value is used for calculation. In 5-10% of cases, the umbilical cord is found entangled around the fetal neck, which can significantly complicate measurement. In such cases, 2 measurements are used: above and below the umbilical cord entanglement site, and the average of these two measurements is used to calculate the risks.

Standards for ultrasound scanning at the end of the first trimester of pregnancy are being developed by the England-based Fetal Medicine Foundation (FMF). In the CIR group of companies, ultrasound is performed according to the FMF protocol.

Additional ultrasound signs of risk for Down syndrome

Recently, in addition to the measurement of spinal cord, the following ultrasound signs have been used to diagnose Down syndrome at the end of the first trimester of pregnancy:

• Nasal bone definition. At the end of the first trimester, the nasal bone not defined using ultrasound in 60-70% of fetuses with Down syndrome and only 2% of healthy fetuses.
• Assessment of blood flow in the Arantium (venous) duct. Abnormalities in the waveform of blood flow in the duct of arantia are found in 80% of fetuses with Down syndrome and only in 5% of chromosomally normal fetuses
• Reduction in the size of the maxillary bone
• Enlarged bladder (“megacystitis”)
• Moderate tachycardia in the fetus

The shape of blood flow in the Arantium duct during Doppler measurements. Top: normal; bottom: with trisomy 21.

Not just Down syndrome!

During an ultrasound scan at the end of the first trimester, fetal contour assessment also helps identify the following fetal abnormalities:

• Exencephaly - anencephaly
• Cystic hygroma (swelling at the level of the neck and back of the fetus), in more than half of cases is caused by chromosomal abnormalities
• Omphalocele and gastroschisis. The diagnosis of omphalocele can be made only after 12 weeks of pregnancy, since before this period a physiological umbilical hernia, which is often detected, has no clinical significance
• Single umbilical artery (in a large percentage of cases combined with chromosomal abnormalities in the fetus)

How are risks calculated?

Special software is used to calculate risks. Simply determining the level of indicators in the blood is not enough to decide whether the risk of developmental abnormalities is increased or not. The software must be certified for use for prenatal screening purposes. At the first stage of computer calculation, the indicator numbers obtained during laboratory diagnostics are converted into the so-called MoM (multiple of median, multiple of the median), characterizing the degree of deviation of a particular indicator from the median. At the next stage of calculation, the MoM is adjusted for various factors (the woman’s body weight, race, the presence of certain diseases, smoking, multiple pregnancies, etc.). The result is the so-called adjusted MoM. In the third calculation step, the adjusted MoMs are used to calculate the risks. The software is specially configured for the methods used in the laboratory for determining indicators and reagents. It is not acceptable to calculate risks using tests done in another laboratory. The most accurate calculation of the risk of fetal abnormalities is when using data from an ultrasound examination performed at 10-13 weeks of pregnancy.

What is MoM?

MoM is an English abbreviation of the term “multiple of median”, which means “multiple of the median”. This is a coefficient showing the degree of deviation of the value of a particular prenatal screening indicator from the average value for the gestational age (median). MoM is calculated using the following formula:

MoM = [Value of the indicator in the patient’s blood serum] / [Value of the median indicator for the gestational age]

Because the indicator value and median have the same units, the MoM value has no units. If the patient’s MoM value is close to one, then the value of the indicator is close to the population average, if it is above one, it is above the population average, if it is below one, it is below the population average. With congenital fetal defects, there may be statistically significant deviations of MoM markers. However, pure MoMs are almost never used in calculating the risk of fetal anomalies. The fact is that in the presence of a number of factors, the average MoM values ​​deviate from the average in the population. Such factors include the patient’s body weight, smoking, race, pregnancy as a result of IVF, etc. Therefore, after obtaining MoM values, the risk calculation program makes adjustments for all these factors, resulting in the so-called “corrected MoM value”, which used in risk calculation formulas. Therefore, in the conclusion forms based on the analysis results, next to the absolute values ​​of the indicators, the corrected MoM values ​​for each indicator are indicated.

Typical MoM profiles in pregnancy pathologies

With various fetal anomalies, MoM values ​​are combined deviated from the norm. Such combinations of MoM deviations are called MoM profiles for a particular pathology. The tables below show typical MoM profiles at different stages of pregnancy.

Typical MoM Profiles - First Trimester

Typical MoM Profiles - Second Trimester

Indications for prenatal screening of the 1st and 2nd trimester for the risk of fetal anomalies

Prenatal screening is currently recommended for all pregnant women. An order of the Ministry of Health of the Russian Federation of 2000 obliges antenatal clinics to conduct biochemical prenatal screening for all pregnant patients in the second trimester of pregnancy for two indicators (AFP and hCG).

Order No. 457 of December 28, 2000 “On improving prenatal diagnostics in the prevention of hereditary and congenital diseases in children”:

“At 16-20 weeks, blood should be taken from all pregnant women to conduct research on at least two serum markers (AFP, hCG)”

The importance of monitoring congenital diseases on an ongoing basis in Moscow is also discussed in the resolution of the Moscow government on the establishment of the city program “Children's Health” for 2003-2005.

“It is advisable to begin in Moscow genetic monitoring of congenital malformations of newborns, prenatal screening for Down syndrome and neural tube defects”

On the other hand, prenatal screening should be a purely voluntary matter. In most Western countries, it is the physician's responsibility to inform the patient about the possibility of such tests and about the purposes, possibilities and limitations of prenatal screening. The patient herself decides whether to have tests done or not. The CIR group of companies shares the same point of view. The main problem is that there is no treatment for the detected abnormalities. If the presence of anomalies is confirmed, the married couple is faced with a choice: terminate the pregnancy or continue it. This is not an easy choice.

What is Edwards syndrome?

This is a condition caused by the presence of an extra 18th chromosome in the karyotype (trisomy 18). The syndrome is characterized by gross physical abnormalities and mental retardation. This is a lethal condition: 50% of sick children die in the first 2 months of life, 95% - during the first year of life. Girls are affected 3-4 times more often than boys. The incidence in the population ranges from 1 case in 6,000 births to 1 case in 10,000 births (about 10 times less common than Down syndrome).

What is the free β-subunit of hCG?

The molecules of a number of hormones of the pituitary gland and placenta (thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and human chorionic hormone (hCG)) have a similar structure and consist of α and β subunits. The alpha subunits of these hormones are very similar and the main differences between the hormones lie in the structure of the beta subunits. LH and hCG are very similar not only in the structure of the α-subunits, but also in the structure of the β-subunits. This is why they are hormones with the same effect. During pregnancy, LH production by the pituitary gland drops to almost zero, and hCG concentrations are very high. The placenta produces very large amounts of hCG, and although this hormone mainly enters the bloodstream in assembled form (a dimeric molecule consisting of both subunits), the free (not associated with the α-subunit) β-subunit of hCG also enters the bloodstream in small quantities. Its concentration in the blood is many times lower than the concentration of total hCG, but this indicator can more reliably indicate the risk of problems in the intrauterine fetus in the early stages of pregnancy. Determination of the free β-subunit of hCG in the blood is also important for the diagnosis of trophoblastic disease (hydatidiform mole and chorionepithelioma), some testicular tumors in men, and monitoring the success of in vitro fertilization procedures.

Which indicator: total hCG or free hCG β-subunit is preferable to use in the second trimester triple test?

Using the free β-hCG subunit assay rather than the total hCG assay provides a more accurate estimate of the risk of Down syndrome, but classic statistical calculations of the risk of Edwards syndrome in a population have used maternal total hCG levels. No such calculations have been made for the hCG β subunit. Therefore, a choice must be made between a more accurate calculation of the risk of Down syndrome (in the case of the β-subunit) and the possibility of calculating the risk of Edwards syndrome (in the case of total hCG). Let us remember that in the first trimester, only the free β-subunit of hCG, but not total hCG, is used to calculate the risk of Edwards syndrome. Edwards syndrome is characterized by low numbers of all 3 indicators of the triple test, so in such cases, both versions of the triple test can be done (with total hCG and with the free β-subunit).

What is PAPP-A?

Pregnancy-associated plasma protein-A (PAPP-A) was first described in 1974 as a high-molecular-weight protein fraction in the blood serum of women in late pregnancy. It turned out to be a large zinc-containing metaloglycoprotein with a molecular weight of about 800 kDa. During pregnancy, PAPP-A is produced by syncytiotrophoblast (tissue that is the outer layer of the placenta) and extravillous cytotrophoblast (islets of fetal cells in the thickness of the uterine mucosa) and enters the mother's bloodstream

The biological significance of this protein is not fully understood. It has been shown to bind heparin and is an inhibitor of granulocyte elastase (an enzyme induced by inflammation), so PAPP-A is believed to modulate the maternal immune response and is one of the factors that ensures the development and survival of the placenta. In addition, it was found to be a protease that cleaves insulin-like growth factor binding protein 4. There are serious reasons to believe that PAPP-A is one of the factors of paracrine regulation not only in the placenta, but also in some other tissues, in particular in atherosclerotic plaques. It is proposed to use this marker as one of the risk factors for coronary heart disease.

Concentrations of PAPP-A in maternal blood continuously increase with increasing gestational age. The greatest increase in this indicator is observed at the end of pregnancy.

Over the past 15 years, PAPP-A has been studied as one of three risk markers for trisomy 21 (Down syndrome) (together with free hCG β-subunit and nuchal translucency thickness). It turned out that the level of this marker at the end of the first trimester of pregnancy (8-14 weeks) is significantly reduced if the fetus has trisomy 21 or trisomy 18 (Edwards syndrome). The uniqueness of this indicator is that its significance as a marker of Down syndrome disappears after 14 weeks of pregnancy. In the second trimester, its levels in maternal blood in the presence of trisomy 21 in the fetus do not differ from those in pregnant women with a healthy fetus. If we consider PAPP-A as an isolated risk marker for Down syndrome in the first trimester of pregnancy, its determination at 8-9 weeks would be most significant. However, free hCG β-subunit is a stable risk marker for Down syndrome at 10–18 weeks, i.e., later than PAPP-A. Therefore, the optimal time for donating blood for a double test in the first trimester of pregnancy is 10-12 weeks.

The combination of measuring PAPP-A levels with determining the concentration of the free β-subunit of hCG in the blood and determining TVP using ultrasound at the end of the first trimester of pregnancy can identify up to 90% of women at risk of developing Down syndrome in the older age group (after 35 years). The probability of false positive results is about 5%.

In addition to prenatal screening for the risk of Down syndrome and Edwards syndrome, in obstetrics the PAPP-A determination is also used for the following types of pathology:

• Threat of miscarriage and stopping the development of pregnancy in the short term
• Cornelia de Lange syndrome.

Risk diagnosis stoppage of fetal development in early pregnancy was the historically first clinical application of PAPP-A determination in blood serum, proposed in the early 1980s. It has been shown that women with low levels of PAPP-A in early pregnancy are at risk of subsequent pregnancy loss and severe forms of late toxicosis. Therefore, it is recommended to determine this indicator at 7-8 weeks for women with a history of severe pregnancy complications.

Cornelia de Lange syndrome is a rare form of congenital malformations of the fetus, found in 1 case in 40,000 births. The syndrome is characterized by mental and physical retardation, heart and limb defects, and characteristic facial features. It has been shown that in this condition, PAPP-A levels in the blood at 20-35 weeks are significantly lower than normal. A study by Aitken's group in 1999 showed that this marker could be used to screen for Cornelia de Lange syndrome in the second trimester of pregnancy, since levels in such pregnant women were on average 5 times lower than normal.

The reagents used to determine PAPP-A and the free β-subunit of hCG are orders of magnitude more expensive than the reagents used for most hormonal parameters, making this test a more expensive test compared to the determination of most reproductive hormones.

What is α-fetoprotein?

It is a fetal glycoprotein produced first in the yolk sac and then in the liver and gastrointestinal tract of the fetus. This is a transport protein in the fetal blood that binds a number of different factors (bilirubin, fatty acids, steroid hormones). It is a dual regulator of intrauterine fetal growth. In an adult, AFP does not perform any known functions, although it can increase in the blood in liver diseases (cirrhosis, hepatitis) and in some tumors (hepatocellular carcinoma and germinal carcinoma). In the mother's blood, the level of AFP gradually increases with increasing pregnancy and reaches a maximum at 30 weeks. The level of AFP in the mother's blood increases with neural tube defects in the fetus and with multiple pregnancies, and decreases with Down syndrome and Edwards syndrome.

What is free estriol?

Estriol is synthesized in the placenta from 16α-hydroxy-dehydroepiantrosterone sulfate supplied from the fetus. The main source of estriol precursors is the fetal adrenal glands. Estriol is the main estrogenic hormone of pregnancy and ensures the growth of the uterus and the preparation of the mammary glands for lactation.

90% of estriol after 20 weeks of pregnancy is formed from fetal DEA-S. The high release of DHEA-S from the fetal adrenal gland is associated with low 3β-hydroxysteroid dehydrogenase activity in the fetus. A protective mechanism that protects the fetus from excess androgenic activity is the rapid conjugation of steroids with sulfate. The fetus produces more than 200 mg of DHEA-S per day, 10 times more than the mother. In the mother's liver, estriol quickly undergoes conjugation with acids, mainly hyaluronic acid, and is thus inactivated. The most accurate method for determining fetal adrenal activity is to determine the level of free (unconjugated) estriol.

Free estriol levels gradually increase as pregnancy progresses and in the third trimester of pregnancy can be used to diagnose fetal well-being. If the condition of the fetus worsens in the third trimester of pregnancy, a sharp drop in the level of free estriol may be observed. Free estriol levels are often reduced in Down syndrome and Edwards syndrome. Taking dexamethasone, prednisolone or metipred during pregnancy suppresses the function of the fetal adrenal glands, so the level of free estriol in such patients often decreases (reduced estriol intake from the fetus). When taking antibiotics, the rate of estriol conjugation in the mother's liver increases and the reabsorption of conjugates from the intestine decreases, so the level of estriol also decreases, but due to the acceleration of its inactivation in the mother's body. For accurate interpretation of the triple test data, it is very important that the patient indicate a complete list of medications taken or taken during pregnancy with doses and timing of use.

Algorithm for prenatal screening in the first and second trimester of pregnancy.

1. Calculate the duration of pregnancy, preferably after consultation with a doctor or with the help of a consultant.

First trimester screening has its own characteristics. It is carried out between 10 and 13 weeks of pregnancy and is quite strictly limited in terms of timing. If you donate blood too early or too late, if you make a mistake in calculating the gestational age at the time of donating blood, the accuracy of the calculation will sharply decrease. Pregnancy dates in obstetrics are usually calculated based on the first day of the last menstruation, although conception occurs on the day of ovulation, that is, with a 28-day cycle - 2 weeks after the first day of menstruation. Therefore, periods of 10 - 13 weeks on the day of menstruation correspond to 8 - 11 weeks on conception.

To calculate the gestational age, we recommend using the obstetric calendar posted on our website. Difficulties in calculating the timing of pregnancy can occur with an irregular menstrual cycle, with pregnancy occurring shortly after birth, with a cycle that deviates from 28 days by more than a week. Therefore, it is best to trust the professionals and consult a doctor to calculate the timing of pregnancy, perform an ultrasound and donate blood.

2. We do an ultrasound.

The next step should be an ultrasound scan between 10 and 13 weeks of pregnancy. Data from this study will be used by the risk calculation program in both the first and second trimester. It is necessary to begin the examination with an ultrasound, since during the examination problems with the development of pregnancy may be revealed (for example, a stop or delay in development), multiple pregnancies, and the timing of conception will be calculated quite accurately. The doctor performing the ultrasound will help the patient calculate the timing of blood donation for biochemical screening. If the ultrasound turns out to be done too early in the pregnancy, then perhaps the doctor recommends repeating the study after some time.

To calculate risks, the following data from the ultrasound report will be used: date of ultrasound, coccygeal-parietal dimension (CPR) and nuchal translucency thickness (NTT) (English abbreviations CRL and NT, respectively), as well as visualization of the nasal bones.

3. Donate blood.

Having the results of the ultrasound and knowing the exact stage of pregnancy, you can come to donate blood. Blood collection for analysis for prenatal screening in the CIR group of companies is carried out daily, including weekends. On weekdays, blood collection is carried out from 7:45 to 21:00, on weekends and holidays: from 8:45 to 17:00. Blood is drawn 3-4 hours after the last meal.

During pregnancy 14 - 20 weeks after the last menstruation (recommended periods: 16-18 weeks), the following biochemical indicators are determined:

• Total hCG or free β-subunit of hCG
• α-fetoprotein (AFP)
• Free (unconjugated) estriol
• Inhibin A

4. We get the result.

Now you need to get the analysis results. The turnaround time for prenatal screening analysis results in the CIR group of companies is one business day (except for the quadruple test). This means that tests taken from Monday to Friday will be ready on the same day, and tests taken from Saturday to Sunday will be ready on Monday.

Conclusions based on the results of the study are issued to the patient in Russian.

Table. Explanations of terms and abbreviations

Report date	Date of computer processing of results
Gestational age	Weeks + days
Date of ultrasound	Date of ultrasound. Usually does not coincide with the date of blood donation.
Fruit	Number of fruits. 1 - singleton pregnancy; 2 - twins; 3 - triplets
ECO	Pregnancy resulted from IVF
KTR	Coccygeal-parietal size determined during ultrasound
MoM	Multiple of median, the degree of deviation of the result from the average for a given period of pregnancy
Accor. MoM	Adjusted MoM. MoM value after correction for body weight, age, race, number of fetuses, presence of diabetes, smoking, infertility treatment using IVF.
NT	Thickness of the collar space (nuchal translucency). Synonym: neck fold. Various reporting options may provide either absolute values ​​in mm or degree of deviation from the median (MoM)
Age risk	Average statistical risk for this age group. No factors other than age are taken into account.
Tr. 21	Trisomy 21, Down syndrome
Tr. 18	Trisomy 18, Edwards syndrome
Biochemical risk	Risk of fetal anomalies after computer processing of blood test data without taking into account ultrasound data
Combined risk	The risk of fetal anomalies after computer processing of blood test data taking into account ultrasound data. The most accurate indicator of risk level.
fb-HCG	Free β-subunit of hCG
DPM	Date of last menstruation
AFP	α-fetoprotein
HCG	General hCG (human chorionic gonadotropin)
uE3	Free estriol (unconjugated estriol)
+NT	The calculation was carried out taking into account ultrasound data
mIU/ml	mIU/ml
ng/ml	ng/ml
IU/ml	IU/ml

Additional Information.

Information for patients: Please note that if you plan to undergo prenatal screening in the CIR group of companies, then ultrasound data performed in other institutions will be taken into account only if there is a special agreement between the CIR group of companies and these institutions.

Information for doctors

Dear Colleagues! In accordance with Order of the Ministry of Health No. 457 and Decree of the Moscow Government No. 572, the CIR group of companies provides services to other medical institutions for prenatal screening for the risk of chromosomal abnormalities. You can invite our employees to come to you with a lecture on this program. To refer a patient for screening, the attending physician must fill out a special referral. The patient can come to donate blood on her own, but it is also possible to have blood taken at other institutions with subsequent delivery to our laboratory, including by our courier. If you want to receive the results of double, triple and quadruple tests of the first and second trimesters of pregnancy, combined with ultrasound data, the patient must come to us for an ultrasound, or we must sign a special agreement with your institution and include your ultrasound specialists in the program, but only after our expert in functional diagnostics will visit your institution and become familiar with the quality of the equipment and the qualifications of the specialists.

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

It is used to identify the risk of developing gross pathologies of the fetus, 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 screening of the first third of gestation you feel confident and competent.

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

What does this show?

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

Reference! Human 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 its 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 amount 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. An ultrasound is performed first - this is a mandatory condition for 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 even drink. If you have a long wait, bring a small snack with you, but you will not be able to eat until after your blood is drawn.
3. On the eve of the study (or better yet, 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 donating blood.

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

Throughout the diet exclude from diet:

• industrially produced sweets, especially chocolate, chewing marmalade and colored dragees;
• tea, coffee, cocoa;
• fish, especially red varieties;
• seafood;
• pickles, canned and smoked products;
• offal;
• meat.

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

In this case, you should consult your doctor.

Vitamins and some other pharmaceuticals may affect test results.

This can cause a lot of anxiety that is unnecessary for the expectant mother.

Decoding the results

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

Table 1. HCG norms.

Both an increase and a decrease in hCG indicates problems in the development of the child or certain conditions of the mother. For example, during pregnancy with twins (triplets) or severe toxicosis, indicators may not fit into the norm. An increase in hCG can be recorded when:

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

Reduced hCG may indicate the presence of conditions such as:

• ectopic pregnancy;
• placental insufficiency;
• high risk of miscarriage;
• Edwards syndrome, which is characterized by many developmental defects.

Let's continue decoding: PAPP-A standards and deviations from them

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

Table 2. RAPP-A standards.

Deviations in the PAPP-A indicator have their own diagnostic significance. An increase in the indicator indicates the bearing of several children, but a decrease may be a consequence of a number of factors:

• fading pregnancy;
• high risk of miscarriage;
• neural tube defect;
• some types of trisomy, the most famous of which is 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 the reason for additional examination of the expectant mother. Blood biochemistry in the first trimester is recommended for all women preparing for motherhood. The procedures are carried out at the woman’s request, and doctors do not recommend ignoring the prescribed examinations.

Risk group

There are patients for whom it is especially important to undergo biochemical screening, since they are at risk:

• age-related risk – pregnant women over 30 years of age (when carrying their first child) and over 35 years of age (when carrying their second and subsequent children);
• women who have previously experienced several missed pregnancies or miscarriages;
• patients who self-administered in early pregnancy drugs that pose a danger to the normal development of the child;
• women who suffered from infectious diseases in the early stages of gestation;
• patients who have relatives with genetic defects or diseases;
• women who have previously given birth to children with genetic abnormalities;
• pregnant women married to a close relative;
• patients who were exposed to radiation before conception or early gestation (or their spouse was exposed);
• ultrasound report indicating genetic abnormalities.

MoM norm

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

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

Where to do it and how much does it cost?

A pregnant woman is referred by a doctor 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 clinic, perinatal or diagnostic center.

Conclusion

Biochemical screening is not a mandatory procedure, but is highly recommended for any pregnant woman. It is this analysis that makes it possible to detect rare, but potentially possible deviations in order to make a difficult decision in time or begin treatment procedures.

During the first trimester of fetal development, many unique processes occur. During this period, the baby develops all internal organ systems. In order to timely diagnose various pathologies during such an important period, ultrasound screening is used.

Why is it carried out?

The introduction of screening examinations in our country occurred quite recently. This was facilitated by high maternal and infant mortality rates. In order to reduce these statistical indicators, specialists from the Ministry of Health have developed special recommendations. They provide for ultrasound examinations several times throughout the entire pregnancy.

Every expectant mother will certainly be interested in the question of what screening is. Literally translated, this term means "screening". During screening, all pregnant women are identified with pathological pregnancy. Expectant mothers who have been diagnosed with any abnormalities should be more closely monitored by doctors.

During this type of study, doctors determine both various developmental pathologies in the baby developing in the mother’s womb, as well as concomitant diseases of the internal genital organs in the mother. This is being done in one study.

If during the examination any deviations were identified, then recommendations are given to the expectant mother be sure to attend the second and third screenings.

With the help of such an examination, you can also determine the sex of the unborn baby - this can be done, as a rule, at 11-12 weeks of pregnancy. Experienced ultrasound specialists can see the sex of the child earlier, but they often make mistakes.

There is no need to rush to find out who “lives” in the tummy.

The baby's intrauterine development undergoes a number of successive stages. By the end of the first trimester, when the first formation of his genital organs occurs, it is necessary to conduct a sex determination study.

Ultrasound examination performed during this period of pregnancy also allows calculate the due date more accurately. Typically this figure is calculated in obstetric weeks. In this case, there is a certain difference between the gestational and obstetric periods. In order to avoid confusion, experts recommend using the term “obstetric” gestational age.

The first trimester is not the best time to exclude all genetic and chromosomal diseases in the fetus. However, it is worth noting that even during this period Some signs of these pathologies can be identified. For this, doctors and scientists have developed a whole set of different ultrasound criteria that are used to draw up a conclusion. They help doctors promptly suspect the first signs of genetic abnormalities in the baby.

Screening ultrasound can also identify certain disturbances of uteroplacental blood flow. This method will identify pathological narrowings or other abnormalities of the blood vessels supplying the fetus. If necessary, an auxiliary method called Dopplerography can be used. It allows you to determine various blood flow pathologies more accurately. During the first ultrasound screening, specialists can also identify quite dangerous pathologies.

Rudimentary brain changes are an unfavorable clinical sign that requires timely diagnosis.

To determine emerging pathologies at this stage of pregnancy, an expert-level ultrasound is sometimes required.

A screening study is a necessary clinical test that allows you to identify dangerous conditions, which can lead to the threat of miscarriage. Specialists, using special ultrasound sensors, look at and identify various pathologies that contribute to the development of fetal hypoxia. This condition is quite clearly visible when using high-resolution devices.

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Deadlines

Doctors recommend that all expectant mothers, without exception, undergo screening. A second ultrasound screening examination is also carried out, as a rule, for absolutely all expectant mothers. The third screening is usually prescribed for certain medical reasons in cases where it is really required.

To obtain more reliable results, experts recommend undergoing ultrasound screening at 11-13 weeks of pregnancy. Usually this study is supplemented by a number of biochemical tests, which are taken 2-3 days before the ultrasound.

Clinical situations are allowed when screening can be delayed by 1-2 weeks. However, a shift in the schedule for screening ultrasound must necessarily be agreed with the obstetrician-gynecologist.

Where can I do it?

A referral for screening is given by an obstetrician-gynecologist who monitors the expectant mother throughout the development of her pregnancy. This medical form indicates the personal data of the pregnant woman, the expected duration of pregnancy, and also makes various notes about her state of health. This direction also indicates the date and time of the ultrasound.

You can also undergo the test in a private clinic. A referral from a doctor is usually not required for this. The expectant mother can sign up for such a study on her own.

Prices for screening ultrasounds in private clinics vary. The average cost of such a study is 2000-4000 rubles. If the examination is carried out using expert-class equipment or by a more qualified specialist, then this diagnostic procedure will cost slightly more. In large cities, the cost of the first screening ultrasound sometimes reaches 8,000 rubles or more.

Proper preparation

To obtain reliable and accurate research results, the expectant mother should be thoroughly prepared for screening. Usually all recommendations are given to a woman at her next appointment with her obstetrician-gynecologist.

Basic preparation in the early stages is usually the same for all pregnant women. However, slight differences may exist. They are usually associated with a full bladder. Most women should not drink a lot of fluids immediately before the diagnostic procedure. Especially if the examination is carried out using the transvaginal method.

However, there are a number of exceptions. In these cases, doctors recommend a few hours before the ultrasound drink about 0.5 liters of liquid. A bladder filled with water pushes the uterus forward, making it more accessible for visualization. Not all women require this special training. If it is still necessary, the doctor will definitely warn the expectant mother about this.

In early pregnancy, no significant preparation is required. Usually, to obtain accurate test results, doctors recommend that expectant mothers follow a special diet. This diet limits all fatty and fried foods.

Dinner on the eve of the diagnostic procedure should be as light as possible. You should not have breakfast before your morning ultrasound. You can only drink a little water.

For expectant mothers suffering from diabetes, especially those with an uncontrolled course, such recommendations cannot be followed. Skipping another breakfast can lead to a critical decrease in blood sugar levels, which is extremely undesirable for both mom and her baby.

A few days before the screening test, pregnant women should exclude all fruits and vegetables from their menu. Also prohibited are any varieties of cabbage, legumes, kvass and any carbonated drinks. All of these foods can cause severe gas.

An intestine filled with gases will not allow an ultrasound specialist to conduct a full examination. In this case, the ultrasound report that the woman will receive after the examination will contain the phrase about echonegativity.

You should not consume a lot of protein foods 2-3 days before the screening examination. Such food, especially in large quantities, also contributes to bloating. It's better that there is food as light as possible, but high in calories and nutrition. Lean poultry or white fish with a side dish of cereals are perfect for this.

Avoiding physical activity is a very important step in preparing for the procedure. Scientists have found that even the usual everyday activities that expectant mothers perform every day can lead to distorted results.

In order to minimize the risk of obtaining an inaccurate test result, You should limit any physical activity. Expectant mothers should replace them with walks in the fresh air at a moderate pace. They will benefit not only the female body, but also the baby who is in her womb.

Any psycho-emotional stress also contributes to disruption of metabolic processes in the body of a pregnant woman. Experts have long discovered one interesting fact: in pregnant women who are suspicious and worried about trifles, during an ultrasound the baby may turn away from the sensor or begin to move actively. In order to fully examine the fetus, doctors strongly recommend that pregnant women not be nervous or worry.

If the expectant mother still continues to smoke while carrying the baby, then on the eve of the study the number of cigarettes smoked should be significantly limited. Doctors have found that nicotine and tars contained in tobacco cause a hypoxic state in the fetus. Also, these chemicals lead to disruption of uteroplacental blood flow, which will be detected by ultrasound.

Various techniques

Ultrasound specialists perform screening studies. They have special training in this branch of medicine. It is better that the first screening is performed by a qualified and experienced doctor who has sufficient experience in conducting such studies.

This will somewhat reduce the risk of possible errors and making an incorrect conclusion after the examination. If, after an ultrasound, the obstetrician-gynecologist has any doubts about the unreliability of the results obtained, then he can refer the expectant mother for re-examination to another specialist.

There are certain situations when a screening test is not performed in a regular antenatal clinic. Expectant mothers with severe concomitant diseases of internal organs or pathologies of pregnancy may be referred for examination to a perinatal center. The specialists of this medical institution will be able to more accurately and efficiently identify all “hidden” pathologies or emerging anomalies in the intrauterine development of babies.

Currently, research can be carried out using several methods. In the early stages it is used in most cases transvaginal. The technique of this procedure involves the use of a special ultrasound probe inserted into the vagina. There is no need to be afraid of this type of examination. With the correct technique, it will not cause the woman any pain or discomfort.

The transvaginal method makes it possible to identify various pathologies in both the mother and the fetus quite effectively and accurately. There are a number of contraindications for this diagnostic procedure; it is not suitable for women with exacerbation of colpitis or vaginitis. In these situations, it is better to resort to an alternative method - the transabdominal one.

In this case, an ultrasonic sensor is used, which the doctor moves over the “pregnant” tummy. This method is also an excellent way to diagnose various defects of intrauterine development. Most expectant mothers prefer this method of ultrasound examination. As a rule, a screening study using this method is also carried out if The patient's husband is present during the diagnostic procedure.

To obtain a high-quality image, a special diagnostic gel. It is transparent and slightly sticky to the touch. The gel is applied to the expectant mother’s tummy area immediately before the procedure.

This substance helps ultrasonic waves to be better reflected and penetrate well into the internal environments of the body. The chemical composition of the gel is completely hypoallergenic and cannot cause allergic reactions.

What to take with you?

If the study is carried out in a women's clinic, then the expectant mother should bring a towel from home. It will be needed to place it on a special couch on which the study will be carried out.

Usually the ultrasound is performed in the supine position. Only in case of certain pathologies of the woman’s uterus, the specialist conducting the examination may ask her to turn on her left or right side. After the procedure, you may need paper napkins. They are necessary to remove residual gel from the abdomen.

If the study is carried out in a private clinic, you do not need to take anything with you. All necessary items are already included in the cost of the procedure and will be provided. The doctor performing the ultrasound may ask for medical documentation. To do this, the expectant mother should not forget to take her card with her.

Evaluation of results

After the study, the doctor who conducted the screening examination will certainly issue his conclusion. It will indicate only those changes that the doctor saw during the study. Also, the conclusion should indicate the sizes of all studied parameters that can be determined at this stage of pregnancy.

Expectant mothers should remember that such a conclusion is not considered a diagnosis. It requires mandatory interpretation by an obstetrician-gynecologist. The decoding can only be carried out by a doctor observing the expectant mother and performing a clinical examination. It is he who determines the presence of pathologies and makes diagnoses.

In some cases, after the examination, the doctor may refer the woman for additional examination. Usually in such a situation some biochemical tests are performed. You may also need to consult a therapist or specialist.

Norms

To assess intrauterine development of the fetus at this stage, doctors use special ultrasound indicators. They were developed by scientists taking into account the characteristics of the physiology and anatomy of the fetus. The use of these indicators helps specialists timely suspect genetic and chromosomal pathologies, and also identify developmental abnormalities in the baby in the early stages:

• Coccygeal-parietal size (CTR) is the baseline indicator used in the first trimester prenatal study. Many experts prefer to use special tables in which the normal values ​​of this indicator are entered. As the baby grows, this parameter increases. This indicates the normal course of pregnancy and optimal intrauterine development of the fetus.

At 11 weeks, this figure is 34-50 mm. It is important to note that these values ​​are averages. By week 12, the values ​​of this indicator already increase to 42-59 mm. After 7 obstetric days, the CTE becomes 51-75 mm.

• Heartbeat- another assessed indicator. It shows how well the fetal heart muscle contracts. The baby’s myocardium begins to work already from the 6th week of its intrauterine development. This ensures that the doctor conducting the study can easily count the number of heartbeats in one minute. Normally, by the 9th week of intrauterine development this figure is already 130-140 per minute. Any deviations from normal values ​​may indicate trouble in the child’s body. In this case, additional diagnostics may be required. Heartbeat is a very important indicator that must be assessed.

• Collar thickness- Ultrasound is also a very important criterion for identifying various gross developmental defects. This indicator is used to predict the risk of various genetic indicators. At the 11th week of intrauterine development, this ultrasound criterion becomes equal to 0.8-2.4. A week later, its values ​​change to 0.7-2.7.
• During the study, doctors can identify a rather dangerous condition called hypertonicity. It can lead to spontaneous miscarriage or threatened miscarriage. In this situation, the obstetrician-gynecologist will refer the expectant mother to hospitalization. To normalize the tone of the uterus, complex therapy and normalization of the daily routine are required.

For many girls, just the phrase about first trimester screening already causes anxiety.

Meanwhile, prenatal fetal screening involves an absolutely painless comprehensive examination.

When is it carried out?

The first is carried out initially in the 1st trimester of pregnancy, that is, on -.

First trimester screening allows you to determine the likelihood of having a baby with congenital malformations (CHD).

What it is

Prenatal ultrasound screening of the fetus is a set of certain diagnostic measures for a pregnant woman.

Screening methods are tests that can be used for large-scale examinations because they are safe and easy to perform.

The results show possible gross anomalies in fetal development and indirect signs of pathologies.

Perinatal fetal screening includes:

1. Special ultrasound screening
   • traditional ultrasound examination (usually called) of the fetus throughout pregnancy. You can see how this procedure is carried out in the photo and video.
   • If you are wondering how much it costs, then know that ultrasound prices vary in each clinic. For example, at Invitro, a study costs approximately 1,500 rubles.
2. Biochemical screening.
   • Aimed directly at identifying the risks of developing syndromes such as Edwards or Down syndrome.

The study involves determining certain specific substances (so-called “markers”) in the blood - they always change in the presence of certain pathologies.

Fetal biochemistry during the first trimester does not make it possible to make an accurate diagnosis.

The results of the examination only to one degree or another make it possible to identify women with a slightly higher risk of any pathology.

And in order to make a more accurate diagnosis, it is necessary to conduct additional examinations (invasive diagnostics, ultrasound).

What is examined in the first trimester

Biochemical analysis involves donating blood, which is tested in the laboratory for the presence of β-hCG - the so-called human chorionic hormone.

Plasma protein A (denoted PAPP), which is associated directly with pregnancy, and AFP (stands for alpha-fetoprotein) are also examined in the blood.

The results of the 1st trimester screening are usually sent to the attending physician from the laboratory, and he then evaluates the data obtained.

Based on whether the analysis is bad or the results are normal, the doctor gives the pregnant woman further recommendations. Refers for a combined diagnosis or prescribes a more detailed diagnosis for the woman.

When calculating the risk of pathology, or vice versa, the norms determine the weight, age, possible hereditary ailments of a pregnant woman, illnesses of the mother, and her bad habits. The results (indicators) depend on all this.

The results and standards of research are assessed in modern laboratories using an automated special program called Prisca. What it is?

Prisca is a computer program. It is Priska who, in accordance with the results of the analysis, evaluates the individual probability of various chromosomal diseases, as well as other possible congenital anomalies of the unborn child.

The optimal time for screening is considered to be 11-13 weeks of pregnancy.

Biochemical screening of the fetus during the first trimester of pregnancy (the so-called “double test”) includes the following studies:

• Free b-subunit of human chorionic gonadotropin (or simply free β-hCG).
• The plasma protein A that is associated with pregnancy is PAPP-A.

However, in order to calculate the risk of trisomy and determine the norms by the Prisca program, ultrasound results are needed.

That is, in order to determine the norm and risk indicators, the doctor will definitely need ultrasound data, which was performed in the 1st trimester, namely, CTR (coccygeal-parietal size) or ultrasound CTR + TVP (examination results (video/photo) with the thickness of the nuchal translucency) .

Indications for biochemical analysis

This examination during the first trimester is mandatory for the following indications:

• When a woman has her first pregnancy after 30 years.
• If you have had several miscarriages before.
• In case the expectant mother has hereditary pathologies.
• If a woman already has children with some kind of genetic pathology.
• When abnormalities/risks are detected during an ultrasound scan of the first trimester.
• In case of severe pathologies during pregnancy, which were confirmed by the results of an ultrasound examination.
• If a woman works in hazardous work.
• In case the marriage is closely related.
• If at the beginning of pregnancy a woman suffered from viral diseases.

Tests for diseases that are directly sexually transmitted are also carried out in the 1st trimester, since they can cause very severe pathologies during the further development of the fetus.

A blood test allows you to:

• detect signs/presence of rubella, as well as viral hepatitis B.
• assess the level of certain hormones in a woman during pregnancy.
• A thorough examination of the general level of glucose in the blood during the entire period of pregnancy allows the doctor to monitor certain blood parameters that are responsible for gestational diabetes mellitus and prescribe treatment in a timely manner.

In turn, an increased level of protein in the blood may indicate the presence of some pathology of the urinary system, kidneys, and even the development of preeclampsia.

How many of these tests need to be taken is determined by the attending physician, depending on the results of the first test.

Decoding the norm

1. The norms for pregnancy-associated plasma protein A range from 0.46 to 8.54 MIU/ml. If the analysis gives a result below normal, this indicates a threat of miscarriage, Down syndrome, as well as Edwards syndrome.
2. Human chorionic gonadotropin beta subunit assay. Normally - 20,000 - 60,000 IU/l.

A bad result is any deviation from the norm.

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

For the expectant mother, the main task is to maintain 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 obtain complete information about the baby’s health, the doctor must check the expectant mother’s blood for hormones and evaluate the results of a general urine and blood test.

Standards for ultrasound diagnostics I screening

During the first prenatal screening in the first trimester, the ultrasound diagnostic doctor pays special attention to the anatomical structures of the fetus, clarifies the gestational age (gestation) based on fetometric indicators, comparing with the norm. The most carefully assessed criterion is the thickness of the collar space (TVP), because 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 nuchal space is usually expanded. Weekly TVP norms are given in the table:

When performing ultrasound screening in 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 ranges from 2 to 3 mm. The size of the baby’s maxillary bone is assessed and compared with the norm, because a noticeable decrease in jaw parameters in relation to the norm indicates trisomy.

During the 1st screening ultrasound, the fetal heart rate (heart rate) is recorded and also compared with the norm. The indicator depends on the stage of pregnancy. Weekly heart rate norms are shown in the table:

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

Fetal age (week)	Average CTE (mm)	Average BPR (mm)
10	31-41	14
11	42-49	13-21
12	51-62	18-24
13	63-74	20-28
14	63-89	23-31

The first screening involves an ultrasound assessment of blood flow in the ductus venosus (Arantius), since in 80% of cases of its violation the child is diagnosed with Down syndrome. And only in 5% of genetically normal fetuses such changes are detected.

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 as the ultrasound screening. Although this is not a mandatory requirement. Blood is drawn on an empty stomach. Analysis of biochemical parameters, which is carried out in the first trimester, is aimed at identifying the degree of threat of genetic diseases in the fetus. For this purpose, the following hormones and proteins are determined:

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

These indicators 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 a given region, the level of indicators fluctuates within the following limits: 0.5-2.2 MoM. When calculating the threat and deciphering the data for analysis, not just the average value is taken, all possible corrections for the anamnestic data of the expectant mother are taken into account. Such an adjusted MoM makes it possible to more fully determine the threat of developing genetic pathology in the fetus.

A blood test for hormones must be performed on an empty stomach and is often prescribed on the same day as the ultrasound. Thanks to the availability of standards for hormonal blood characteristics, the doctor can compare the test results of a pregnant woman with the norms and identify a deficiency or excess of certain hormones

HCG: risk assessment

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

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

Standards for pregnancy-associated plasma protein-A

This is a specific protein that the placenta produces throughout the gestational period. Its growth corresponds to the period of pregnancy development and 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 reason to suspect the threat of developing a chromosomal abnormality in the fetus (Down and Edwards disease). The norms for PAPP-A indicators during normal gestation are shown in the table:

However, the level of protein associated with pregnancy loses its informative value after the 14th week (as a marker of 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 the normal level - as in the blood of a woman with healthy pregnancy.

Description of the first trimester screening results

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

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

low values ​​of protein-A (PAPP-A) and elevated beta-hCG – a risk of developing Down syndrome in a child;
low levels of protein-A and low beta-hCG are a threat to Edwards disease in the baby.
There is a fairly accurate procedure to confirm a genetic abnormality. However, this is an invasive test that can be dangerous for both mother and baby. To clarify the need to use this technique, ultrasound diagnostic data are analyzed. If there are echo signs of a genetic abnormality on an ultrasound scan, the woman is recommended to undergo invasive diagnostics. In the absence of ultrasound data indicating the presence of a chromosomal pathology, the expectant mother is recommended to repeat the 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 identified using a biochemical blood test. However, if the ultrasound does 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 obtained 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 chromosomal abnormalities of the fetus (low, threshold, high). It is important to remember that the resulting transcript of the results is only a forecast, not a final verdict.

Quantitative expressions of levels vary in each country. For us, a value of less than 1:100 is considered a high level. 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 considered to be the risk of having a baby with developmental defects in the range from 1:350 to 1:100.

The threshold level of threat means that the child may be born sick with a risk of 1:350 to 1:100. At a threshold level of threat, the woman is sent to see a geneticist, who gives a comprehensive assessment of the data obtained. The doctor, having studied the parameters and medical history of the pregnant woman, identifies her in the risk group (with a high or low degree). Most often, the doctor recommends waiting until the second trimester screening test is performed, and then, having received a new threat calculation, come back for an appointment to clarify the need for invasive procedures.

The information described above should not frighten expectant mothers, and there is also no need to refuse to undergo first trimester screening. Since most pregnant women have a low risk of carrying a sick baby, they do not require additional invasive diagnostics. Even if the examination showed poor fetal condition, it is better to find out about it in a timely manner and take appropriate measures.

If research has revealed a high risk of having a sick child, the doctor must honestly convey this information to the parents. In some cases, invasive research helps clarify the situation with the fetus's health. If the results are unfavorable, it is better for the woman to terminate the pregnancy early in order to be able to bear a healthy child

If unfavorable results are obtained, what to do?

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

First of all, it is unlikely to be worth the time and money to undergo re-screening at another laboratory. If the risk analysis shows a ratio of 1:100, you cannot hesitate. You should immediately contact a geneticist for advice. The less time is lost, the better. With such indicators, a traumatic method of confirming the data will most likely be prescribed. At 13 weeks, this will be an analysis of chorionic villus biopsy. After 13 weeks, it may be recommended to perform a cordo- or amniocentesis. Analysis of chorionic villus biopsy provides the most accurate results. The waiting period for results is about 3 weeks.

If the development of chromosomal abnormalities of the fetus is confirmed, the woman will be recommended to have an artificial termination of pregnancy. The decision is, of course, up to her. But if the decision is made to terminate the pregnancy, then the procedure is best performed at 14-16 weeks.