The second screening during pregnancy is a decoding of indicators and norms. Screening of the second trimester: when they do it, interpretation of the results, indicators of the norm and deviations Screening of the 2nd trimester in which week

The second screening during pregnancy is a comprehensive diagnosis, which includes both ultrasound and the determination of several marker hormones in the blood of the expectant mother.

It is performed for all women to confirm or refute the results of their first screening, as well as for acute indications for screening ultrasound during pregnancy.

There are nuances of preparation for the study.

Data decoding is carried out according to the same principle as in the screening of the first trimester.

Should pregnant women undergo a second screening?

The study is carried out according to the same indications as in the first trimester:

1. future parents are relatives
2. there has been an acute bacterial or viral disease
3. the mother suffers from one (several) of those diseases that can be genetically transmitted: diabetes mellitus, diseases of the musculoskeletal system, oncopathology
4. one of the future parents has a genetic (chromosomal) disease in the family
5. had a miscarriage or spontaneous preterm birth in this woman
6. one or more children with developmental anomalies have already been born
7. had a history of fetal death before delivery.

2nd trimester screening will also be ordered if:

1. the first ultrasound of pregnant women, which was done at 14 weeks and later (for various reasons), revealed a pathology of fetal development (if this study was earlier, the woman is sent for screening of the 1st trimester)
2. in the period of 14-20 weeks, an acute infectious disease developed
3. the woman was diagnosed with a tumor later than 14 weeks of her pregnancy.

In the latter cases, the pregnant woman is referred to a geneticist, who decides whether to carry out a complete perinatal examination of the 2nd trimester.

There may be situations when it will be sufficient to conduct a second ultrasound examination in the conditions of the perinatal center (that is, biochemical screening will not be carried out).

What is seen on ultrasound in the second trimester

• the lengths of the bones of the same name on both sides, the volumes of the head, chest, abdomen - the second ultrasound screening allows us to conclude that the development is proportional and consistent with the gestational age
• ventricles and cerebellum
• spine
• facial structures in front and profile (especially with 2 screening ultrasound during pregnancy, the nasolabial triangle and eye sockets are examined)
• ventricles, atria of the heart, places of origin of large vessels from it (diagnosis of the 2nd trimester shows if there are any abnormalities in the development of the cardiovascular system)
• kidneys and bladder
• stomach and intestines.

What does the second prenatal examination by maternal and temporary (provisional) organs show:

1. location of the placenta
2. placenta thickness
3. structure and maturity of the placenta
4. the number of vessels in the umbilical cord
5. amount of amniotic fluid
6. condition of the cervix and walls of the uterus
7. condition of the uterine appendages.

Based on the second screening ultrasound during pregnancy, it is concluded whether there are fetal malformations or not.

How to prepare for the second perinatal diagnosis

• diagnostic ultrasound (according to the sensations and nature of the conduct, it does not differ from the usual examination during pregnancy)
• screening test: this word refers to the analysis of venous blood for a certain amount of hormones.

It is no longer necessary to prepare for an ultrasound examination at this time: the intestines, no matter how many gases there are, are pushed back by the pregnant uterus. And the full bladder, which served as a window for the ultrasound, has now been replaced by amniotic fluid.

Before donating blood at the 2nd screening during pregnancy, preparation is needed: during the previous day, you deny yourself the following products:

• chocolate
• cocoa
• citrus
• seafood
• fatty and fried foods.

In addition, before you donate blood, you need at least 4-6 hours without eating at all. You can only drink water for 4 hours, but without gas and in an amount of not more than 150 ml.

3rd trimester screening does not require any preparation at all.

When does this study take place?

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How the study is done

The study of pregnant women consists of the following manipulations:

1. Ultrasound diagnostics during pregnancy. This procedure in the second trimester of pregnancy is carried out only transabdominally, that is, through the skin of the abdomen. To do this, you simply lie down on the couch, open your stomach, and the doctor will drive the sensor along its front wall. It does not cause pain or discomfort.
2. Biochemical screening 2nd trimester. You come on an empty stomach to the laboratory that conducts this study, they take a few milliliters of blood from a vein. There you provide the results of ultrasound diagnostics, fill out personal data.

So they do the diagnosis of the 2nd trimester. The received indicators will be processed by the program - you can pick up the results only after 2 weeks.

Deciphering the results

2 screening during pregnancy consists of several indicators, each of which has its own norm.

Biochemical diagnostics

The indicators of the second screening, its biochemical part, are hormone levels:

• human chorionic gonadotropin (hCG)
• estriol (E3)
• α-fetoprotein (AFP)
• and in the event that not a triple, but a quadruple test is carried out, the level of inhibin.

The results of the second study normally depend on the duration of pregnancy. Norms of diagnostics of the second trimester:

The indicators of the second examination during pregnancy are evaluated by the MoM value - the average value, which is calculated taking into account the age, body weight and the region where the pregnant woman lives. The screening score of a given woman is divided by the value obtained from studies in a large sample of women of the same age living in the same area.

Examination data of the 2nd trimester is deciphered as follows:

• if the hormone is in the range of 0.5-2.5 MoM, this is considered normal
• if the results of the second “sifting” during pregnancy show a figure less than the lower limit (0.5) or higher than 2.5, this requires additional consultation with a geneticist.

Deciphering the diagnosis of the second trimester is to determine the degree of risk for a particular pathology (it is written as a fraction).

Norm - if the risk is less than 1:380(for example, 1:500 or 1:1000). A high risk is considered to be 1:250-1:360 for any pathology (the calculation is for Down syndrome, neural tube defect, Edwards, Patau). In this case, a consultation with a geneticist is required.

At a risk of 1:100, you may be offered an invasive diagnosis, that is, confirmation of the alleged anomaly by obtaining the chromosome set of the fetus itself.

Indicators of ultrasound diagnostics

2 pregnancy screening evaluates:

• indicators of fetometry (measurement of the size of the fetus)
• the structure of the face is assessed: there should be a normal size of the nasal bone, there should not be a cleft of the face, both eyeballs should be normally developed
• structure of internal organs: heart, brain, spine, stomach and intestines, lungs, bladder and kidneys
• lung maturity
• attention is drawn to the number of fingers on each limb
• amount of amniotic fluid
• thickness and maturity of the placenta
• the condition of the cervix and body of the uterus is examined
• attention is drawn to the uterine appendages.

Based on a visual assessment of the external and internal organs of the fetus, the correspondence of the size of the fetus to its gestational age, the results of an ultrasound examination of the 2nd trimester are issued: does the baby correspond to its term, does it have developmental anomalies.

Normal readings for some weeks

11 week

Screening at week 11 is still included in the concept of the first, and not the second examination during pregnancy.

• HCG \u003d 20-90 thousand honey / ml
• PAPP = 0.45-3.73 mU/ml
• KTR on average - 43 mm
• BPD average - 17 mm
• collar zone 0.8-2.4 mm
• the bones of the nose should already be there, but its size is not determined.

13 week

Diagnosis at 13 weeks of gestation also applies to the diagnosis of the first trimester. His rules:

• HCG \u003d 15-60 thousand honey / ml
• PAPP = 1.03-6.0 mU/ml
• nasal bone - 3 mm
• KTP - 51-87 mm
• collar area thickness = 0.7-2.7 mm
• BPD = 26 mm.

14 week

Screening at 14 weeks pregnant is a routine ultrasound. Blood is not taken at this time. Research norms:

• BPR = 27-29 mm
• nasal bone: 3.4-3.6 mm
• KTP = 76 mm
• head circumference (OG) - 95-106 mm
• girth of the abdomen -78 mm
• thigh: 12-15mm
• shoulder: 13 mm.

16 week

Examination at 16 weeks of gestation. This is the first week of the second stage of prenatal diagnosis. Norms of "sifting" the second trimester of pregnancy for this week:

• HCG \u003d 10-58 thousand mU / ml
• ɑFP = 15-95 U/ml
• E3 = 5.4-21 nmol/l
• BDP = 31-37 (35 - on average) mm
• LZR = 41-49 mm
• OG = 112-136
• coolant = 88-116 mm
• thigh:17-23mm
• shoulder: 15-21
• forearm: 12-18
• drumstick: 15-21 mm
• amniotic water index (IAI): 80-200 mm.

20 week

Screening at the 20th week of pregnancy is normally represented by the following indicators:

• HCG \u003d 1.6-49 thousand honey / ml
• ɑFP = 27-125 U/ml
• E3 \u003d 7.8-28 nmol / l
• BDP = 43-53
• LZR = 56-68
• belly: 124-164 mm
• head circumference: 154-186
• thigh: 29-37
• shoulder length: 26-34
• forearm: 22-29
• drumstick: 26-34
• placenta thickness: 16.7-28.6mm
• placental maturity - "0"
• IAI \u003d 93-130mm.

Screening at 20 weeks is the last time you can still determine hormones in the blood. If you had an indication, but you didn’t, you can only rely on ultrasound, and later on cardiocurrent and dopplerography, to make sure that the fetus is alive.

22 week

Screening at 22 weeks of gestation consists only of ultrasound diagnostics. Hormones in this period are no longer determined. If malformations that are incompatible with life or cause significant disability are identified, this period is the deadline for making a final decision on prolonging the pregnancy. This is so because after 23 weeks, medical termination of pregnancy will be called preterm birth.

Normal readings this week (in millimeters):

• nasal bones - 5.8-6.1 each
• BDP = 48-60
• OG = 178-212
• coolant = 148-190
• hip: 35-43
• lower leg: 31-39
• forearm: 26-34
• shoulder: 31-39.

Answers to the most common questions about the study

IN.:Is it true that the second set of diagnostics during pregnancy was canceled?

ABOUT.: According to the Order of the Ministry of Health of the Russian Federation of November 1, 2012 N 572n, with normal indicators of the first biochemical study, screening of the 2nd trimester is carried out only as an ultrasound scan in a perinatal center.

This is necessary in order to exclude late-appearing anomalies in the development of the fetus. That is, if the PAPP and hCG levels in the first trimester were normal, the risk is above 1:380, then 2nd screening during pregnancy is performed only as an ultrasound diagnosis.

If a high risk (1:100 or more) was detected in the first trimester, a woman must be consulted by geneticists. If necessary, an invasive diagnosis is performed, or the question of the advisability of conducting a full screening study of the II trimester before such a study is being decided.

IN.:Increased hCG at the second screening. What does this mean?

ABOUT.: It can be under such conditions:

1. multiple pregnancy
2. toxicosis
3. diabetes
4. down syndrome
5. incorrectly calculated gestational age.

IN.:What is a bad 2nd trimester result?

ABOUT.: This means that in this case there is a high risk that a particular child may have Down syndrome or other pathology at the chromosomal level. Look at the form, in which pathology the “badness” is suspected. This is determined by the column in which the number 1:380 or less is written (for example, this entry applies only to Edwards syndrome).

IN.:How is it that the first screening is good and the second is bad?

ABOUT.: There can be 2 answers to this question:

1. there are defects that appear later, that is, closer to the second trimester (the period of 16-20 weeks was chosen precisely because of them)
2. the accuracy of the results of the 2nd screening is lower than in the first such study.

IN.:What if a bad second screening?

ABOUT.: Seek genetic counseling.

Description

Material under study Serum

Home visit available

The study is performed for screening examination of pregnant women in order to assess the risk of fetal chromosomal abnormalities - trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), as well as neural tube defect (NTD). Quantification of research results is carried out using PRISCA software.

Attention! For this study, the results of ultrasound are required!

Biochemical screening of the second trimester of pregnancy "triple test" of the second trimester consists of the following studies:

Determination of the concentration of these markers is used for screening of pregnant women in the second trimester of pregnancy in order to assess the risk of chromosomal abnormalities and fetal neural tube defects. The study is carried out between 15 and 20 weeks of pregnancy. The optimal timing for 2nd trimester screening is between 16 and 18 weeks of pregnancy.

Conducting a comprehensive examination at a period of 11-14 weeks of pregnancy, including ultrasound and determination of maternal serum markers (free beta-subunit of hCG and PAPP-A), followed by a complex software calculation of the individual risk of having a child with a chromosomal pathology, is recommended for all pregnant women by order of the Ministry of Health RF dated November 01, 2012 No. 572n (“Procedure for the provision of medical care in the field of obstetrics and gynecology”). If screening results are normal in the 1st trimester, a single AFP determination can be used in the 2nd trimester to rule out neural tube defects (see AFP Test #92), or a complete 2nd trimester PRISCA profile. A triple biochemical test with a complex software calculation of risks in the 2nd trimester may be especially appropriate for borderline risk assessment results during 1st trimester screening, and also if for some reason the 1st trimester screening was not carried out on time.

PRISCA (developed by Typolog Software, distributed by Siemens) is an EU-certified (CE-certified) and registered for use in the Russian Federation program that supports risk calculation for screening examinations of the 1st and 2nd trimesters of pregnancy. The risk calculation is carried out using a combination of biochemical markers informative for the corresponding period and ultrasound indicators. 1st trimester ultrasound data performed at 11-13 weeks of gestation can be used to calculate risks in the PRISCA program during 2nd trimester biochemical screening. At the same time, the PRISCA program will carry out an integrated calculation of risks, taking into account the value of NT (thickness of the nuchal space of the fetus) relative to the median values ​​of this indicator for the gestational age on the date of its measurement in the 1st trimester.

The accuracy of the indicated individual data, the qualifications of the ultrasound provider in performing prenatal screening ultrasound measurements, and the quality of laboratory tests are essential for correct calculations.

Preparation

It is preferable to take blood in the morning on an empty stomach, after 8-14 hours of a night fasting period (you can drink water), it is permissible in the afternoon 4 hours after a light meal.

On the eve of the study, it is necessary to exclude increased psycho-emotional and physical activity (sports training), alcohol intake, an hour before the study - smoking.

Screening of the first trimester is optimal at 11-13 weeks, the second trimester - at 16-18 weeks. 1st trimester ultrasound data can be used to calculate risk in 2nd trimester biochemical screening.

Indications for appointment

Screening examination of pregnant women in the second trimester of pregnancy to assess the risk of chromosomal pathologies and a defect in the neural tube of the fetus, especially appropriate in case of borderline results of the calculated risk of chromosomal pathology during screening of the 1st trimester, and also if the screening examination of the 1st trimester was not carried out on time.

To complete the study, you must fill out.

Interpretation of results

The interpretation of test results contains information for the attending physician and is not a diagnosis. The information in this section should not be used for self-diagnosis or self-treatment. An accurate diagnosis is made by the doctor, using both the results of this examination and the necessary information from other sources: history, results of other examinations, etc.

The results of the survey are issued in the form of a report form. It indicates the data used in the calculations, provides the results of the studies, adjusted values ​​of MoM. In the conclusion, quantitative indicators of the risk degree for trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome) and neural tube defect (NTD) are indicated, which reflect the frequency of occurrence of the corresponding types of pathology with similar examination results and individual data. For example, a risk ratio of 1:6250 means that the statistical probability of having a child with the corresponding pathology is one in 6250 pregnancies with similar individual data. The PRISCA program has set conditional thresholds for identifying a high-risk group - a frequency above 1/250 for trisomy 21 (Down syndrome), above 1/100 - for trisomy 18, AFP MoM above 2.5 - for a neural tube defect.

The results of calculating the risk of fetal chromosomal abnormalities based on screening biochemical studies and ultrasound indicators are only statistical probabilistic indicators that are not the basis for making a diagnosis, but may serve as an indication for the appointment of further special research methods. According to the current recommendations of the Ministry of Health of the Russian Federation, when a pregnant woman is found to have a high estimated risk of chromosomal abnormalities in the fetus (individual risk of 1/100 and higher), the obstetrician-gynecologist sends her to a medical genetic consultation (center) for medical genetic counseling and establishing or confirmation of the diagnosis using invasive examination methods to establish the fetal karyotype.

The use of complex (ultrasound + biochemical) screening, according to a number of studies, makes it possible to detect Down's syndrome in the fetus of pregnancy in 85 - 90% of cases with 5% of false positive results. Comprehensive screening helps to identify not only the risk of a fetal chromosomal abnormality, but also the overall risk of pregnancy pathology.

Pregnancy is a crucial period in a woman's life, proceeding according to special rules. They determine not only the nature of nutrition, the daily routine, the mode of physical activity, but also require regular monitoring of the condition of both the expectant mother and the child in her womb. After the first major examination, performed at 11-13 weeks, the time comes to undergo a 2nd trimester screening, which includes a second ultrasound and a biochemical blood test. Its purpose is to confirm or refute the development of pathologies, to detect their direct and indirect markers. So, who is shown such a diagnosis? What does it include, and how are the indicators deciphered? How to properly prepare for the procedures, and how do they occur?

In order to obtain the most accurate information, the second screening is carried out in a time frame clearly defined by the standards:

• biochemical blood test - from the 15th to the 20th week, while the interval from the 16th to the 18th week is considered the optimal period. It was at this time that the information content of the study to determine the biochemical formula and composition of hormones is maximum;
• perinatal ultrasound screening of the 2nd trimester: the ideal time is 19-24 weeks. It is performed after passing biochemistry. As a rule, ultrasound is prescribed in the period from the 19th to the 22nd week, and if complications are suspected, a second scan from the 22nd to the 24th week may be indicated. For special indications, the period of planned screening can be shifted to earlier dates and carried out starting from the 16th week.

It is not necessary to take the above studies at the same time. You can distribute them over time so as not to be subjected to excessive load. At the same time, it is worth remembering that if ultrasound can be rescheduled or repeated at any time, then there are strict limits for taking a blood test, due to the variability of its composition over the course of pregnancy.

Who is shown the second screening, and can it be waived

Screening 2 is a set of examinations that the Ministry of Health strongly recommends that every pregnant woman undergo at the appropriate weeks. It is mandatory for representatives of the risk group, that is, subject to at least one of the following conditions:

• the parents of the unborn child are close relatives;
• an infectious disease transferred in the early stages, especially in the period of 14-20 weeks;
• a genetic disease in the anamnesis of one of the parents, older children;
• previous pregnancies ended in miscarriages;
• previously born children with developmental delay or pathologies of the nervous system;
• serious deviations from the norm identified during the first screening, the threat of disruption of gestation;
• the age of the future woman in labor is over 35 years;
• oncopathology detected after the 14th gestational week;
• radiation exposure to which the father or mother of the child was exposed on the eve of conception or immediately after it.

If an oncological disease is detected, the patient is referred for a consultation with a geneticist, who usually prescribes additional examinations: a second ultrasound or an additional biochemical blood test. This is done to assess the danger of the patient's condition and decide on the advisability of prolonging or terminating the pregnancy.

The second screening is not forced. If the expectant mother fears that the examination may harm the health of the child and her own, she has the right to write a written refusal to carry out the diagnosis. The doctor is obliged to provide an application form upon request. At the same time, he must explain to the patient all the risks to which she exposes both herself and the baby.

What is looked at at the second screening during pregnancy

The tasks of the second screening include the study of not only fetometric parameters, but also the functional characteristics of the vital organs of the fetus, namely:

• spine, skull and other bones of the skeleton;
• facial features (eyes, nose, mouth);
• kidneys, bladder and other elements of the genitourinary system;
• myocardium and the entire circulatory system;
• digestive organs, including the stomach and intestines;
• brain, spinal cord and related structures;
• components for calculating BDP (biparietal size), LZR (frontal-occipital size), OB (abdominal circumference), OG (chest circumference), length of paired bones.

With a good location, the diagnostician is able to determine the sex of the unborn child according to the gender characteristics formed at the time of the study.

In addition to analyzing the development of the baby's organs and systems, an assessment is made of the state of the mother's body, since the viability of the fetus depends on it. The examination program includes scanning:

• placenta, its location, thickness, size, structure, maturity;
• amniotic waters, their quantitative characteristics;
• umbilical cord, the presence of all the main vessels;
• uterus, cervix and appendages.

During the procedure, the position of the fetus in the placenta is assessed.

Based on the results obtained, the doctor draws conclusions about the presence or absence of pathologies during pregnancy, the sufficiency of blood and oxygen supply, the correct development of the fetus, as well as the presence or absence of a threat to the health and life of the child and mother.

Preparation for the survey

The screening schedule consists of two main procedures: 2nd trimester ultrasound and blood chemistry.

If ultrasound scanning will be carried out in the abdominal way, then the most filled bladder is required to visualize the area under study. This can be achieved by drinking at least one liter of water. If an intravaginal examination is planned, then, on the contrary, it is recommended to refrain from excessive fluid intake.

Before you donate blood, you need to prepare more thoroughly. In order to ensure the maximum informational value of the results, a day before the sampling of biological material, one should refuse fatty, spicy and fried foods, fish and other seafood, chocolate and cocoa, citrus fruits. It is forbidden to eat 5-6 hours before the visit to the laboratory. In case of severe thirst, it is allowed to drink no more than one glass of water without gas, but no later than 30-40 minutes before the manipulation. If possible, the patient should avoid stressful situations.

How is the procedure carried out

The second screening begins with an ultrasound scan.

Planned prenatal ultrasound screening is no different from the standard one. During the procedure, the woman is comfortably located on the couch, the diagnostician lubricates the skin in the places of its contact with the sensor with a hypoallergenic gel. Information is read through the anterior abdominal wall with the abdominal form of the study, through the vagina - with the transvaginal. After a few minutes, the transcript of the results is given to the patient in her hands.

Before performing a biochemical blood test, the observed must provide a transcript of the ultrasound and a special questionnaire. Based on this information and a preliminary conversation with the pregnant woman, the doctor decides on the need to determine the concentration in the blood of a number of additional elements. The sampling of material for research is done from a vein. Its analysis is performed using a special computer program. The test results are ready within two weeks.

What is included in the list of surveys

The second perinatal screening involves two mandatory procedures:

• ultrasound examination;
• biochemical blood test.

In some cases, for example, if a future woman in labor had to perform an unscheduled blood test at an earlier date, she will only be scheduled for a second ultrasound.

A complete biochemical test as part of this routine study involves determining the concentration in the blood of four elements:

• hCG (human chorionic gonadotropin) - a hormone produced by chorion tissues after embryo implantation;
• AFP (alpha-fetoprotein) - a protein that is produced by the liver and gastrointestinal tract from the 3rd week of the existence of the embryo;
• EZ (free estriol) - a hormone that is synthesized by the liver and adrenal glands of the fetus;
• inhibin A - a specific female hormone, the concentration of which varies depending on the timing of pregnancy and the condition of the fetus.

Such an analysis is called a quadruple test. Compared to the first trimester screening program, the measurement of the last two indicators, free estriol and inhibin A, is added to the tasks of the quadruple test.

If there are no indications for studying the concentration of inhibin A in a pregnant woman, then only hCG, AFP and EZ are analyzed. Such a study, accordingly, is called a triple test.

Factors Affecting Results

In the course of any examination, both false positive and false negative results can be obtained. Factors that can distort the results of screening (especially for a blood test for hormones) are:

• chronic diseases of the expectant mother, including diabetes mellitus;
• bad habits (drinking alcohol and drugs, smoking);
• overweight or underweight pregnant. In the first case, the figures are overestimated, in the second case they are underestimated;
• the age of the patient is over 35 years;
• pregnancy with twins, triplets and so on;
• conception performed according to the IVF method;
• taking certain hormonal drugs.

If dangerous pathologies are identified, in order to confirm or refute the diagnosis, the woman will be assigned additional non-invasive (repeated ultrasound) or invasive (cordocentesis, amniocentesis) examinations. Depending on the results obtained, the doctor will recommend leaving or terminating the pregnancy. The patient makes the final decision.

Interpretation of the results of analyzes and ultrasound and normative indicators of the second trimester

After the patient has passed all the mandatory procedures included in the second screening, the supervising obstetrician-gynecologist proceeds to decipher the results. It is based on data from tables that show the norms of all indicators in accordance with the gestational age. The doctor must compare the values ​​​​of hormones and protein in the patient's blood with normal ones, on the basis of which to draw conclusions about the health of the mother and fetus. Based on the results of ultrasound, they evaluate and compare with age standards:

• fruit size;
• facial features (state of the eyeballs, nasal bones, absence of pathologies);
• internal organs (heart, lungs, kidneys, liver, gastrointestinal tract, and so on);
• amniotic waters (their quantity and content);
• placenta (its thickness and structure).

Blood

The norms of indicators of blood biochemistry within the 2nd screening depend on the duration of pregnancy. Their values ​​are given in the table.

When performing a quadruple test, the blood levels of an inhibitor of FSH secretion are assessed. The concentration of the hormone in a singleton pregnancy should not exceed 500 pg / ml, in a multiple pregnancy - 600 pg / ml.

MoM

A general assessment of biochemical screening is made based on the average values ​​of the indicators. It is expressed in the value of MoM - a coefficient showing the degree of deviation of the results from the norm. It is calculated as the ratio of the obtained value of the indicator in the blood serum to the median, characteristic for a given period of pregnancy. The MoM formula also contains variables such as:

• body weight of the patient;
• her age;
• territory of residence.

Normal values ​​are considered to be in the range of 0.5-2.5 MoM. If this requirement is not met, a woman needs to consult a geneticist, since such a discrepancy indicates an increased risk of having a child with Down syndrome, Patau, Edwards and a number of others.

A risk ratio not exceeding 1:380 is considered acceptable. If the predicted figure refers to the interval 1:250…1:360, it is necessary to listen to the opinion of a specialist in genetic abnormalities. At high risk (above 1:100), additional studies, including invasive ones, are strongly recommended. The probability of having a child with disabilities in this case is very high.

Body length and weight of the fetus

The beginning of the second trimester is marked by the intensive development of the fetus, so it is difficult to speak of growth and weight standards at this time. As a rule, the length of a child's body ranges between 10 and 16 cm. At the same time, doctors pay attention not to absolute indicators, but to an increase per week.

The second planned ultrasound scan during pregnancy does not make it possible to directly determine the weight of the fetus in the womb. It is calculated by formulas, and the result obtained has a serious error. On average, by the 20th week, body weight is 300 grams, and by the 22nd week it can reach 450 grams.

Circumference of the abdomen and head

To say that the pregnancy is developing correctly, the coolant (abdominal circumference) must correspond to the following values, depending on the period:

• 16 weeks - 88-116 mm;
• 17 weeks - 93-131 mm;
• 18 weeks - 104-144 mm;
• 19 weeks - 114-154 mm;
• 20 weeks - 124-164 mm;
• 21 weeks - 136-176 mm;
• 22 weeks - 148-190 mm.

OG (head circumference) during normal development should be equal to:

• 16 weeks - 112-136 mm;
• 17 weeks - 121-149 mm;
• 18 weeks - 131-161 mm;
• 19 weeks - 142-174 mm;
• 20 weeks - 154-186 mm;
• 21 weeks - 166-198 mm;
• 22 weeks - 178-212 mm.

Biparietal (BPR) and fronto-occipital (LZR) dimensions of the fetal head

BDP and LZR are two key indicators that indicate the absence of deviations in the baby. Depending on the term, the BDP should vary within:

• 16 weeks - 31-37 mm;
• 17 weeks - 34-42 mm;
• 18 weeks - 37-47 mm;
• 19 weeks - 41-50 mm;
• 20 weeks - 43-53 mm;
• 21 weeks - 45-56 mm;
• 22 weeks - 48-60 mm.

The following frameworks are established for LZR:

• 16 weeks - 41-49 mm;
• 17 weeks - 46-54 mm;
• 18 weeks - 49-59 mm;
• 19 weeks - 53-63 mm;
• 20 weeks - 56-68 mm;
• 21 weeks - 59-71 mm;
• 22 weeks - 63-75 mm.

Length of bones: lower leg, femur, shoulder and forearm

The correct formation of the child's skeleton is evidenced by the compliance with the accepted standards of DG (length of the bones of the lower leg), DB (length of the femur), DP (length of the humerus), DPP (length of the bones of the forearm). The established average values ​​corresponding to the gestational age are shown in the table.

Fetometric parameters

During the ultrasound, which is performed in the second trimester of pregnancy, such key fetometric parameters as coolant, OH, BDP, LZR and the length of tubular bones are studied and analyzed. If the examination revealed a deviation from the median value, this is not an unconditional marker of pathology or deviation. The reasons may be different: there is a possibility of an error in determining the date of conception, or the parents have a slender physique, so growth retardation may be caused by heredity. All fetometric characteristics must be analyzed as a whole. It is not the absolute values ​​of the indicators that are important, but the proportional relationship between them.

Brain and spine

Usually, two axial sections are used to study brain structures using ultrasound: transventricular and transcerebellar. Rarely, a transthalamic section is chosen. During the examination, the diagnostician looks at the cerebellum, lateral ventricles, a large cistern and the cavity of the transparent septum. The shape of the head and the texture of the brain are also evaluated. In a healthy child, all examined elements should correspond to normal X-ray anatomy.

The main section for studying the state of the spine is longitudinal. It is very important that the three centers of ossification of the vertebrae are visible. The doctor examines the bones for the absence of an open spinal hernia, sacral agenesis, and other abnormalities. As a rule, such pathologies are combined with disorders identified in the brain. With ultrasound, attention should also be paid to the skin over the ridge. If necessary, the inspection continues with the selection of the cross section.

Respiratory system

At the time of the woman's examination, the fetal respiratory system is already fully formed. During the examination, the main attention is paid to the condition of the lungs and their degree of maturity. So, normally, each lung should occupy about a third of the cross section of the chest.

The level of formation of this organ is estimated in the ratio of its echogenicity in comparison with the liver. There are three levels of maturity:

• 0 - echogenicity of the lungs is lower than that of the liver;
• 1 - the echogenicity of the compared organs is approximately equal;
• 2 - echogenicity of the lungs is higher than that of the liver.

Heart

During an ultrasound, the doctor examines the condition and functionality of the heart. In this case, the following indicators are evaluated:

• organ location. Normally, at this time, it occupies a third of the chest;
• position of the axis of the heart;
• size and condition of the heart chambers;
• the shape of the interventricular septum;
• tissue structure - myocardium, pericardium, enrocardium.

Pay attention to the frequency and rhythm of heart contractions. The first parameter should normally be equal to 140-160 beats per minute.

Digestive system

By the time of the second scheduled ultrasound, the fetus is already fully formed and functioning digestive system: esophagus, stomach, pancreas, intestines. It is important to carefully examine the entire gastrointestinal tract: find the connection between the stomach and the esophagus, make sure that all organs are present, and that there are no hyperechoic elements in them.

urinary system

The formation of the kidneys in the fetus begins already on the 22nd day from the moment of conception, and by the end of the second trimester this process is completely completed. Ultrasound allows you to accurately identify the pathology of the urinary system. Normal kidney sizes are:

• 18 weeks - 16-28 mm;
• 19 weeks - 17-31 mm;
• 20 weeks - 18-34 mm;
• 21 weeks - 21-32 mm;
• 22 weeks - 23-34 mm.

The ratio of the size of the renal pelvis to the size of the entire pyelocaliceal system should not differ by more than 5 mm.

In most pregnant women, the adrenal glands of the fetus begin to be visualized on ultrasound around the 20th week. Their size is about 9-10 mm. The correct ratio of the size of the kidneys and adrenal glands is 0.48-0.65. In this case, the left adrenal gland should be larger than the right.

Signs of pathologies

The second screening is designed to identify and prevent the development of abnormalities and diseases.

Important markers of genetic abnormalities and other abnormalities are the following signs found during ultrasound scanning:

• lag in the development of the fetus;
• omission of the placenta;
• polyhydramnios or oligohydramnios, the content of flakes and suspensions in the amniotic waters;
• thickening of the walls of the placenta, its early aging;
• disproportionate ratio of fetometric characteristics;
• irregular shape of the facial bones, especially the nasal;
• ventriculomegaly, or enlargement of the lateral ventricles of the brain;
• cerebral vascular cyst;
• pyelectasis, or expansion of the renal pelvis, and others.

Indicators of violations are also deviations of the results of a biochemical test.

An increase in hCG levels may indicate a risk of developing Down syndrome or Klinefelter, and a decrease in it may indicate Edwards syndrome.

On the defects of the nervous system, necrosis of the liver, the absence of the esophagus, umbilical hernia and Meckel's syndrome, the deviation of the AFP value from the average to the large side indicates. The reverse violation is a symptom of Down and Edwards syndromes, and may also indicate the death of the fetus or an incorrectly determined date of conception.

An elevated E3 level can indicate both problems with the mother's liver and kidneys, as well as a large baby or multiple pregnancy. But the insufficiency of this hormone is a symptom of infection, placental insufficiency, hypertrophy of the adrenal glands, trisomies, anencephaly and a marker of the risk of premature termination of gestation.

Excess levels of inhibin A in the blood may indicate fetoplacental insufficiency, oncoprocess, genetic abnormalities, and insufficient - the threat of self-abortion.

Possible diseases

Some pathologies are previously detected at the first prenatal screening and according to the results of a blood test. The second scheduled screening ultrasound is designed to confirm or refute such suspicions. With its help, trisomy is diagnosed (Down, Edwards, Patau, de Lange syndromes), arising from an extra chromosome in one of the rows, anomalies of the central nervous system, facial structures, and so on.

Down syndrome

Down syndrome is one of the most common chromosomal abnormalities in the fetus. It develops due to the occurrence of an extra chromosome in the 21st chromosome row. Children born with this pathology have a specific appearance, suffer from various diseases of the internal organs, and lag behind in development. Very often, such people live relatively short lives.

Down syndrome can be suspected already at the stage of blood biochemistry. It is evidenced by an increased level of hCG and a reduced level of AFP and estriol.

On ultrasound, the described pathology is characterized by thickening of the collar zone and shortening of the nasal bone.

neural tube defect

There are several types of neural tube defects:

• spina bifida, when a protrusion of the spinal cord occurs at its base;
• anencephaly - areas of the brain and skull that have not formed in the upper part, the absence of hemispheres;
• encephalocele, in which the brain and membranes protrude through the cranial vault;
• Chiari malformation - penetration of brain tissue into the spinal column.

Such pathologies are perfectly visualized with ultrasound and are manifested by an increase in the level of AFP (less often, a drop in free estriol).

Edwards syndrome

The cause of the manifestation of Edwards syndrome is a genetic mutation associated with the duplication of chromosomes in the 18th pair. The disease is manifested by the peculiarities of appearance and its inherent disturbances in the functioning of internal organs, motor skills and the psyche. Unfortunately, the mortality rate in the first year of life in children born with such a defect reaches 90%.

On ultrasound screening, the pathology is manifested by characteristic anomalies in the structure of the skull and face, deviations in the structure of the skeleton, urinary and cardiovascular systems. In the results of a blood test, reduced protein, hCG and estriol are noted.

False results

The second screening is characterized by a high degree of objectivity. Its diagnostic reliability according to various sources is estimated at 60-90%. The probability of obtaining false positive results does not exceed 2.5%.

Distorted data are obtained if the patient is obese (the content of hormones in the blood increases), diabetes mellitus (hCG decreases), is pregnant with twins, and also if IVF has taken place (the protein level is lower by 10-15%, hCG is overestimated).

A normal result does not guarantee the birth of a healthy baby, because some physical defects or mental retardation may be caused by unidentified factors.

How often can I do an ultrasound in the second trimester

The regulatory documents of the Ministry of Health of Russia establish the mandatory conduct of three ultrasound examinations during pregnancy (one in each trimester at a clearly defined time frame). With problem bearing, the number of such procedures can be more than ten.

Ultrasound is recognized as a safe form of diagnostics of pregnant women. The doses and intensity of ultrasound used are not capable of harming the human fetus. Even WHO officially allowed four sessions during pregnancy, but, if possible, not earlier than the 10th week.

Further actions

If, based on the results of the second prenatal screening, the doctor made a conclusion about the normal course of pregnancy, the excellent condition of the expectant mother and a healthy child, the next group of examinations will take place from the 30th to the 32nd week as part of the third scheduled screening.

If pathologies or an increased risk of their development are detected, the patient may be referred for repeated ultrasound or invasive diagnostic procedures: chorionobiopsy, cordocentesis, amniocentesis. In some cases, it is necessary to observe a geneticist up to delivery.

If a condition is diagnosed that means the child is not viable, deformed, retarded in physical and mental development, termination of pregnancy may be recommended. The patient makes the final decision.

The course of the gestation period is subject to systematic monitoring. In the second trimester, the expectant mother is given another one. Based on the results, a conclusion is drawn up on the state of health of the woman and the child. In order to prevent intrauterine pathologies of the fetus, timely diagnosis is important. There is a need to study the optimal timing of screening.

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The essence of 2nd trimester screening

During the pregnancy period, an obstetrician-gynecologist may prescribe a 2nd trimester screening for a woman. It is then that the question arises of what it is and why it is carried out. Such research is intended identify pathologies in embryonic development. The level of possible complications is determined. Among the main goals of fetal screening at this stage are:

• determination of pathologies not detected during the diagnosis of the first trimester;
• clarification of the reliability of diagnoses made during the first stage of gestation;
• diagnosing the level of possible complications;
• detection of physiological disorders in the development of the embryo.

According to statistics, the first screening study is more accurate and reliable than the second procedure.

However, single results cannot be the basis for a definitive diagnosis. Upon completion of the second screening, the dynamics of fetal development indicators can be traced.

Due to this, trends are identified for the formation of conclusions.

It is important to remember that this event is not mandatory when carrying a fetus. It is prescribed only for those patients who are at risk.

Among the factors that serve as a reason for increased attention, it is customary to include:

• the age of the patient is over 35 years;
• early exposure of future parents;
• the presence of heredity with identified pathologies;
• detection of genetic pathologies in firstborns;
• the course of viral diseases during the first three months of gestation;
• the presence in the anamnesis of cases of spontaneous, abortive intervention and the birth of dead children;
• the occurrence of conception between blood relatives;
• susceptibility to harmful addictions (use of alcohol-containing and narcotic substances);
• the use of drugs that are unacceptable during gestation;
• identification of difficult working conditions.

If nothing threatens the condition of the pregnant woman, the event is not held. Be aware that this is a study woman can pass at will.

Information about what 2 pregnancy screening is, how many weeks it is carried out, is provided by the attending physician. The obstetrician-gynecologist during the consultation covers the main aspects of the procedure. Due to this, exciting moments are eliminated, which sometimes constitute a danger to the condition of the pregnant woman.

Perinatal screening of the 2nd trimester allows you to determine the following pathologies:

• abnormal development of the cardiovascular system;
• failure in the process of building the respiratory system;
• abnormal formation of the gastrointestinal tract;
• defect in the spinal cord and brain;
• pathological structure of the organs of the endocrine system;
• defective limb development.

In case of detection of phenomena that pose a danger to embryonic development, may be requested. The variant of resolving the situation depends on the results obtained, as well as the individual characteristics of the maternal organism.

Structure 2 screening

If there are indications, a woman is assigned to mandatory 2 screening during pregnancy.

What is included and what does the second screening show in the course of pregnancy - the main points of interest to patients.

As part of the second screening event, an ultrasound examination (ultrasound) of the body is carried out and a biochemical blood test is taken.

During the ultrasound examination, the following are subject to study:

• the structure and parameters of the fetal face (the eyes, nose, oral cleft, ears are identified; the development of the eyeball is examined; the size of the nose bone is determined);
• embryo parameters (represents a fetometric analysis);
• the level of embryonic development of the organs of the respiratory system;
• analysis of internal fetal organs for pathological structure(of interest are the brain and spinal cord, heart, gastrointestinal tract, urinary system);
• the number of fingers in a child on the upper and lower extremities;
• parameters of the fetal bladder (maturity level and thickness of the placenta);
• the state of the reproductive system in a pregnant woman (the area of ​​\u200b\u200bthe uterus, cervix, tubes and ovaries is analyzed);
• parameters of the amniotic fluid (the fact of leakage of amniotic fluid is established or refuted).

In addition to the above aspects, which shows ultrasound diagnostics, to be specified. This is achieved due to the greater severity of primary sexual characteristics.

Diagnosis implies a transabdominal principle. The sensor of the device is in contact with the skin in the abdomen. Before starting the procedure, a gel-like agent is applied.

Note! The data that ultrasound shows are supported by the results of a biochemical blood test. In the absence of violations according to the results of ultrasound markers, blood biochemistry does not give up.

Among the markers of fetal chromosomal pathology to be assessed during ultrasound, there are:

• slowdown or lack of embryonic development;
• oligohydramnios;
• ventriculomegaly;
• pyelectasis;
• discrepancy with the normative value of the size of the tubular bone;
• discrepancy between the parameters of the nasal bone;
• cyst in the vascular plexus of the brain.

Biochemical screening 2nd trimester

Biochemical screening of the 2nd trimester is blood test for the presence of specific compounds in it.

The concentration of these substances may vary depending on the identified violations.

The main goal for which biochemical screening of the 2nd trimester is carried out is to identify:

• failure in the formation of neural tubes in the brain and spinal cord;
• chromosomal anomalies (presented as Edwards syndrome and Down syndrome).

In the course of studying the composition of the blood, attention is focused on the level of:

• indicators of alpha-fetoprotein (AFP);
• human chorionic gonadotropin (hCG);
• free estriol;
• inhibina A.

A blood test gives an idea of ​​the dynamics of the condition. The diagnosis is made taking into account other research measures. Invasive measures, ultrasound diagnostic measures may be needed.

Experts are of the opinion that biochemical diagnostics is required for every pregnant woman. Even under the condition of a favorable course of pregnancy in the early stages, the expediency of conducting a study does not lose its relevance.

Screening preparation

Preparing for screening in the 2nd trimester does not require much effort. For ultrasound diagnostics, it is customary to highlight the following list of tips:

• The event can be held regardless of the time of day.
• The fullness of the bladder is not able to distort the results (by the second trimester, the volume of amniotic fluid increases; the level of amniotic fluid eliminates the need to fill the bladder).
• The fullness of the intestine does not play a role (by the time of the procedure, this organ is exposed to an enlarged uterus).

• Blood analysis must give up on an empty stomach(eating on the eve of the process may affect the accuracy of the results).
• The exclusive use of purified water is allowed.
• It is required to exclude the intake of fried foods, spicy dishes, flour products, sweets.
• Restriction of allergenic products (chocolates, citrus fruits, strawberries or other foods that cause an allergic reaction in a patient) is supposed.
• It is better to donate blood in the first half of the day (otherwise, a state of dizziness, nausea, vomiting may occur without the possibility of suppressing them with drugs).

The preparatory phase must be carried out with positive emotions and attitude. This is especially true when pathologies are detected after the first screening.

It should be remembered that the screening test is painless. Regardless of the patient's sensitivity threshold, there are no uncomfortable sensations. The procedure does not pose a danger to the health of the child being born.

When is the best time to do

Screening of the 2nd trimester is an exciting stage in the course of pregnancy.

The further bearing of the fetus depends on its results. That is why the question arises when it is better to do the procedure.

The optimal timing is stage from the 16th to the 20th week. Often, when asked when it is better to do this complex, experts recommend a 17-week period.

This feature is associated with sufficient development of the fetus. Its parameters allow you to detail individual areas of interest to assess its condition.

Note! The accuracy of the values ​​is directly dependent on such a category as the timing of the research. A correctly calculated period allows for the most reliable screening of the 2nd trimester. Otherwise, the obtained data cannot be used to clarify the diagnosis.

Useful video: second screening during pregnancy

Conclusion

Carrying out screening diagnostics facilitates the process of bearing a fetus. Knowing what a second pregnancy screening is, what specialists look at, frees a pregnant woman from unreasonable fears. Confidence in the condition of the fetus guarantees peace of mind for the expectant mother.

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In the second trimester of pregnancy, expectant mothers may be offered to undergo another screening, which, in terms of a set of procedures, is even simpler than the previous one - in the first trimester.

The second prenatal screening is a less popular procedure and is performed only if indicated or at the request of the woman in labor.

Since 2012, the Order of the Ministry of Health has slightly changed the screening regime for pregnant women in the second trimester. If the results of an early examination conducted in the period from the 11th to the 14th week of pregnancy are favorable, then the future woman in labor will only receive a referral for a period of 22-24 weeks of pregnancy.

However, if desired, the mother can also undergo a paid biochemical examination.

The second stage of full screening testing is supposed to go through future women in labor who are at risk for bearing a fetus with intrauterine incurable malformations, for the same reasons as in the first trimester:

• if the father of the child is a close relative of the mother;
• if the mother is over 35 years old;
• if the parents are carriers of hereditary diseases;
• in the family there are cases of bearing children with congenital malformations;
• if the mother's obstetric history is aggravated by prolonged or complications in previous periods of gestation, fetal death;
• if, against the background of the current pregnancy, an acute infectious or bacterial disease occurred in the early stages;
• if the expectant mother takes drugs that are contraindicated during pregnancy.

And also if:

• the first screening during pregnancy showed a threshold or high level of probability that the fetus has malformations;
• if an acute infectious or bacterial disease in the mother happened after the 14th week;
• if a neoplasm was detected in the mother in the second trimester.

What is included in second trimester screening?

The second screening also looks at the individual risks of giving birth to a fetus with genetic abnormalities.

The main task of second trimester screening is to “weed out” mothers for whom the risk of bearing a baby with developmental disabilities is not lower than the threshold and offer them a more thorough and in-depth examination, for example, invasive, as a result of which the woman will be recommended to decide whether to continue or terminate the pregnancy.

This test is called "triple" because the values ​​of three of its constituent indicators are subjected to research:

alpha-fetoprotein

ACE is a protein in the blood serum of the embryo. It begins to be produced from the third week after conception in the yolk sac, and from the second trimester (after reduction of the yolk sac) in the liver and in the gastrointestinal tract of the unborn child.

This specific protein is involved in providing the fetus with nutrients, protects against the influence of estrogen and aggression from the mother's immune system.

AFP produced by the fetus enters the mother's blood through the placenta.

Therefore, from the moment of conception, the level of alpha-fetoprotein in the blood of a woman increases markedly, and from the second trimester of pregnancy, its values, in combination with other indicators, are informative as markers of the state of fetal development and the course of the gestation process.

total hCG or free β-hCG subunit

In the blood of a woman, a few days after fertilization, it is determined by the laboratory.

This hormone is produced by the chorion (the precursor of the placenta), and from the second trimester it is produced by the formed placenta. HCG is called the hormone of pregnancy, because it is "responsible" for maintaining pregnancy and its successful course, regulating the production of female hormones.

For purposes, it will be more indicative to determine the level of the hCG β-subunit, because. the content of this particular hCG subunit in the blood of a woman after conception increases significantly and reaches a maximum value by the 10th week of pregnancy, after which it decreases markedly.

Whereas for the purposes of the second screening, the information content of determining hCG and the β-subunit of hCG will be equivalent.

Free estriol

The female sex hormone, the activity of which, under the influence of hCG, increases sharply in the blood of a woman after fertilization. But the main "supplier" of estriol to the mother's body during pregnancy is the placenta and fetal liver.

The level of estriol affects the state of uteroplacental blood flow, the development of the uterus, as well as the formation of ducts in the mammary glands of the expectant mother.

If there is a technical and technological capability in the laboratory, mommy can be given a “quadruple” test - they will analyze the content of inhibin A in the blood.

Inhibin A

A specific female hormone, an increase in the level of which in a woman's blood is characteristic of pregnancy. Its content in the blood of the expectant mother depends on the timing and condition of pregnancy and the fetus. It is produced by the ovaries of a woman, and in the state of expectation of the baby - by the placenta and the body of the embryo.

Inhibin A for calculating the risks of fetal malformations is rarely taken into account in the second screening study - mainly when the previous 3 parameters do not give an unambiguous picture.

It is obvious that all indicators involved in the screening test, as a rule, are unique for the state of pregnancy, and therefore, according to the level of their production in accordance with generally accepted indicators at different stages of pregnancy, one can judge the well-being of the development of pregnancy and the fetus.

When do they do it: timing

It is important not to be late with all diagnostic procedures before the term when abortion is allowed for medical reasons - up to the 22nd week.

Expert ultrasound, which allows you to assess the state of the internal organs of the grown crumbs, and, possibly, to identify signs of chromosomal developmental anomalies, if any, as well as the state of the fetoplacental complex, is considered informative no earlier than the 22nd - 24th week.

Therefore, during the second screening of the period of bearing a child, the data of the ultrasound protocol carried out as part of the first screening are used.

If, for some reason, the results of a screening ultrasound for 11-14 weeks of pregnancy are not available, then it should be done at least to clarify information about the gestational age and whether the size of the fetus corresponds to its age.

The timing of the second screening (triple test) is very limited. A biochemical test should be taken strictly from the 16th week to the 6th day of the 18th week of pregnancy. ]

Screening norms for the second trimester during pregnancy

The values ​​taken as norms for the parameters studied in the laboratory analysis of the patient's blood, as part of the second screening, may vary, depending on the ethnic composition of the region in which the laboratory is located and for which the settings of the diagnostic computer program are made.

Taking into account all the influencing factors, MoM will be calculated - the ratio of the laboratory value of the studied blood indicator to the average value during normal pregnancy, all other things being equal. MoM values ​​that are normal for screening purposes are universal for all laboratories and are in the range: 0.5 - 2.5 MoM.

Screening norms for the second trimester (boundary values ​​of biochemical markers) are as follows:

What do deviations from the norm show?

Factors influencing the deviations of the values ​​of indicators determined during biochemical screening of the second trimester from the reference values ​​may indicate not only the development of fetal chromosomal abnormalities.

It may also indicate violations or features of the development of the pregnancy itself, as well as the state of maternal health.

It should be noted that among the reasons for deviations from the norms of hormonal values, there may also be an incorrectly established gestational age, non-compliance with the rules for preparing for screening by a pregnant woman, violations of the rules for collecting material for analysis, etc.

Evaluation of the results of the second screening

To evaluate the values ​​of screening markers honey. institutions use computer programs specially developed for diagnostic purposes, which calculate the risks of certain deviations, taking into account the values ​​of all test indicators in the aggregate, including the data of the ultrasound protocol. This is called combined screening.

Moreover, the result is determined with an amendment for each specific case.

The individual history of the expectant mother is taken into account: multiple pregnancy, pregnancy due to IVF, bad habits, weight, age, chronic diseases, etc.

In addition, when screening the second trimester, the database for calculating screening risks also enters the primary results of the examination conducted during the period of 10-14 weeks of gestation. Only such an integrated approach for the purposes of non-invasive prenatal diagnosis of possible pathologies of fetal development is the most reliable.

It makes no sense to consider each indicator separately for the purposes of a screening survey.

Firstly, the list of possible reasons that affect the difference between each individual component and the average statistical norm is quite large.

Secondly, not always even a significant non-falling into the boundaries of the normal values ​​of any one hormone being determined necessarily indicates screening risks.

For example, even with multiple deviations of the AFP level from the norm, if you ignore the values ​​of other indicators, the risk of fetal deformities is possible only in 5% of cases. And with prenatal diagnosis of a disease such as Patau's syndrome, the level of AFP will not cause concern at all.

Therefore, only with a cumulative analysis of the values ​​of all biochemical markers can one make assumptions about the likelihood of developing congenital malformations of the fetus.

Reliability of results

Before going for screening to identify the risks of developing incurable fetal defects, the expectant mother should understand that the purpose of screening tests is not to make a diagnosis, but to determine the likelihood of an event occurring.

Even with a high risk of developing any pathology of the fetus, identified by the results of screening of the second trimester, which is 1:100 and lower, this means that with similar values ​​of screening markers, one out of a hundred women gave birth to a child with developmental abnormalities due to chromosomal anomalies.

And even in the case of 1:2, much more “risky”, the probability of an adverse event is 50%. And it is this probability that is predicted with maximum accuracy - up to 90% - by diagnostic programs.

However, with a “bad” first screening, a re-examination in the second trimester will definitely be recommended for a combined assessment of the results and increase the reliability of forecasts.

If the first screening is bad, and the second is good, or vice versa, and if both screenings confirm a high risk of malformations of the unborn baby, then the woman will have a meeting with a geneticist to discuss the need for invasive diagnostics (amneocentesis).

In any case, before the invasive procedure, an early expert ultrasound at 20 weeks should be performed and, based on the results of the ultrasound, further actions should be discussed with the geneticist.

It should be borne in mind that some malformations do not give anatomical abnormalities visible on the ultrasound screen (about 20% of cases).

With unfavorable prognosis for the first screening and, on the contrary, favorable for the second one, and also in the opposite case, one should not rush to claim that the tests give false results.

This could happen due to the influence of any unaccounted factors on the screening indicators: the woman taking hormonal drugs, stressful pregnancy, food excesses, etc.

It should also be borne in mind that for assessing the risks of developing trisomy 21 chromosome (Down syndrome) in the fetus, the results of early screening are considered more reliable. While the risks of developing Edwards syndrome, for example, or neural tube defects, are more reliable to assess after the 16th week.

And this means that the identification of the risks of developing some defects at the first screening is uninformative.

If the results of screening are important for future parents, you should not neglect the conversation with a geneticist who is able to professionally and individually assess the likelihood of certain events based on screening data.

The need for a second biochemical screening

In recent years, doctors have abandoned the general examination of women in the second trimester. And this is not at all because it is not needed and not important.

In fact, one should understand what goal the state pursues by paying for women to undergo very expensive procedures included in screening.

Particular attention in screening is paid to identifying the risks of developing Down syndrome. And there is an explanation for this.

• Down syndrome is the most frequently diagnosed disease, relative to other pathologies of fetal development, due to a chromosomal error - about 1: 700;
• Malformations of the fetus due to trisomy on the 21st chromosome may not manifest themselves in any way on an ultrasound scan made later than the period indicative of this disease (10-14 weeks of pregnancy). Whereas other chromosomal abnormalities in the fetus, in most cases, entail anatomical defects, determined by ultrasound;
• Down's syndrome is a disease quite compatible with life, while the suffering of children born with other incurable malformations, as a rule, ends within the first year of life.

And this last point is, apparently, the main reason that women who are at high risk of having a baby with Down syndrome are sent for screening of the second trimester of pregnancy.

Indeed, often, parents are not ready to take on the burden of caring for a special child and raising him and refuse the baby at birth. Thus, all cares, including financial ones, to provide for a born little man, who is not capable of independent life in the future, are assigned to the state.

The results of the screening allow predicting the risk of developing congenital incurable abnormalities in an unborn child and, at a high level of such risk, enable family members to decide whether they are ready to accept and love a baby who will need maximum attention and special care.

Depending on the decision of the family council, the expectant mother will be asked to determine the karyotype of the fetus in order to finally verify the development of a chromosomal abnormality in the fetus or exclude it.

Of course, if a woman is ready to endure, give birth and take care of a baby with developmental disabilities, then screening does not make sense at all.