Screening data. Screening in the first trimester of pregnancy - what you need to know about the norms and results. Screening - what is it?

Many women who are preparing to undergo their first examinations during pregnancy are interested in what the 1st trimester screening standards are.

If you want to know what indicators characterize the fetus at this time, what the result of ultrasound and tests may be, and how to properly prepare to donate blood, then read this article.

First trimester screening is an important undertaking that should not be neglected.

The test results that you will receive after undergoing it will allow doctors to assess the actual condition of your child and make the right conclusions regarding the further course of pregnancy.

Women in the first trimester of pregnancy are often surprised to learn that the first screening of their condition and fetal development is carried out through two procedures: ultrasound diagnostics and blood sampling.

Most often, at this stage, an ultrasound of the fetus is performed abdominally - through the abdominal walls of the mother's abdomen.

A woman who is going to undergo such an ultrasound should prepare for it - drink several glasses of cool, still, clean water.

Fluid entering the bladder will create some stress on the uterus, and an ultrasound will be performed to obtain more accurate data.

The sonologist performing the ultrasound evaluates the development of the child, which should correspond to his gestational age, and the biometry of the fetus, comparing the actual size of the fetus with the normative ones.

After this, the doctor measures various parameters, the analysis of which can give an informative conclusion about the actual condition of the fetus, confirm or exclude the presence of pathologies of its development.

The optimal time for the first pregnancy screening is the twelfth to thirteenth week of its development. The result of the study consists of several factors.

Below you can see the average data, which are normative for children of this gestational age.

The standard thickness of the collar space, measured at this time, should range from one and a half to two and a half millimeters.

If the thickness of the VP is greater, doctors may suspect various chromosomal abnormalities of the fetus. You can clarify their presence by visiting a number of additional prenatal non-invasive diagnostics.

It is important to pay attention to the fact that TVP is measured only at the first pregnancy screening, since it cannot be determined at subsequent ultrasounds.

In addition, the following fetal indicators are analyzed (at the twelfth to thirteenth week of pregnancy):

1. the size of the nasal bone is at least three millimeters;
2. heart rate - from one hundred fifty to one hundred seventy beats per minute;
3. blood flow spectrum in the fetal ductus venosus;
4. the size of the baby's upper jaw bone;
5. bladder capacity.

An ultrasound result, signaling possible deviations from the norm, may indicate the presence of various gene abnormalities, in particular Down syndrome.

Fetal biometry carried out at the twelfth to thirteenth gestational week of development must meet the following standard indicators:

• biparietal size - from fourteen to twenty-six millimeters;
• coccygeal-parietal size - from thirty-two to seventy-four millimeters;
• head circumference - from sixty-two to ninety-eight millimeters;
• abdominal circumference - from fifty-one millimeters to seventy-eight millimeters;
• thigh bone length - from five and a half to twelve and a half millimeters;
• the child’s height is from ninety to one hundred and ten millimeters;
• weight - around seventy grams.

HCG norms during the first screening (blood test)

The best time to take a blood test is the day on which you will undergo an ultrasound.

In order for the data to be as accurate as possible, you should prepare for blood sampling - do not eat for twelve hours before the procedure, and also follow a mandatory diet.

Eliminate from your diet:

• chocolate and other sweets;
• meat, fish, smoked meats;
• carbonated drinks.

Doctors who draw blood from pregnant patients send it to a special laboratory.

At this point it is tested for two indicators:

1. human chorionic gonadotropin (hCG);
2. RARR-A.

Ideally, screening for the first trimester of pregnancy should take place within one day. Early in the morning you must donate blood from a vein, then undergo an ultrasound procedure.

Thanks to this, the result of double diagnosis will be accurate and will help doctors reliably determine the condition of the fetus.

Human chorionic gonadotropin is a hormone that is present in the blood of every pregnant woman. Its quantity allows you to determine the exact gestational age of the fetus.

The normal level of human chorionic gonadotropin in the twelfth to thirteenth week of pregnancy is from thirteen and a half to one hundred and fifteen ng/ml.

Elevated levels of hCG may indicate various genetic abnormalities in the development of the child.

However, the level of hubbub, which differs more from the norm, may indicate other factors:

• multiple pregnancy;
• acute toxicosis;
• intoxication with various drugs taken by a woman during the first trimester of pregnancy;
• maternal diabetes mellitus;
• various tumor neoplasms of unknown origin;
• the presence of Down syndrome in the fetus;
• hydatidiform mole.

In turn, a reduced level of human chorionic gonadotropin may indicate:

• for ectopic pregnancy;
• for a frozen pregnancy;
• the presence of a threat of miscarriage;
• for the presence of Edwards syndrome in the fetus.

If the test result causes serious concern to the gynecologist supervising the pregnancy, then most likely he will prescribe an additional invasive procedure, consisting of chorionic villus biopsy.

This procedure will make it more likely to clarify the condition of the fetus and confirm or exclude the presence of anomalies in its development.

PAPP-A norms during the first screening (blood test)

PAPP-A is a protein compound that is produced by the outer layer of the placenta of a pregnant woman.

The presence of this protein is recorded in the blood throughout pregnancy. PAPP-A levels increase with each gestational stage of development of the child in the womb.

If the result of a blood sample tested for the presence and level of PAPP-A worries the doctor, the doctor will prescribe a number of additional prenatal non-invasive diagnostics.

The result of a blood test for the presence of PAPP-A, carried out during the first pregnancy screening, should range from one to eight and a half mU/ml.

A lag in PAPP-A levels from normative values ​​corresponding to the current gestational age of the fetus may indicate the presence of Down or Edwards syndrome.

The result of an analysis that reveals an increased level of PAPP-A may signal a missed pregnancy or a very real threat of miscarriage.

It should be remembered that the best time to donate blood tested for PAPP-A is the twelfth to thirteenth week of pregnancy.

After the fourteenth gestational week, the result of the PAPP-A analysis may lose its information content.

It is best if you go through all stages of first trimester screening at one medical facility.

Computer programs developed to systematize data obtained during examinations, which are used in various medical institutions, have different settings.

Therefore, to maintain the reliability of the data, you should sign up for blood sampling and ultrasound at the same clinic. You can undergo these tests both in a city and in a private hospital.

If the blood biochemistry result that you receive after taking the tests alerts the doctor, despite the fact that the first ultrasound does not cause any complaints, then the doctor will recommend that you undergo additional examination.

From the moment of conceiving a child, every expectant mother begins to tune in to many tests, analyzes and medical consultations. No matter how frightening all this may be for pregnant women, without such research it is impossible to identify likely serious risks associated with the health of the fetus. Throughout the entire period, it is necessary to adhere to the entire prevention program, which is prescribed by the treating gynecologist.

It is important not to neglect the recommended tests. Biochemical screening is considered one of the most mandatory tests. Despite the unattractive name, this analysis is very useful for building a picture of the health of the unborn child.

What it is

Biochemical blood screening is a rather narrow-profile analysis. Applies to primary and secondary test categories. Detects signs of diseases such as hepatitis B and rubella. In the extended version, the analysis allows you to determine the presence of syphilis and HIV infection in the blood.

Nevertheless, the main function of screening is considered to be to identify the fetus’s predisposition to pathologies. Also, the results of the analysis clearly demonstrate how certain diseases will develop in the embryo in the future. In this regard, the attending physician builds a step-by-step program for the treatment or prevention of pathologies.

Biochemical screening allows you to determine the Rh factor and blood type. These characteristics will be extremely useful in the future if the mother needs proper treatment. To prescribe serious hormonal drugs, it is important to know the Rh factor of the pregnant woman and her child.

Screening at a later date can reveal the likelihood of so-called gestational diabetes.

Who is the procedure indicated for?

Every pregnant woman should undergo biochemical screening. Some experts question the urgent need for the analysis. However, it is unlikely that anyone will guarantee that none of the expectant mothers have serious genetic disorders. The fact is that many women are not even aware of a pathological malfunction in their body, as well as infections. Some mothers have a hereditary predisposition to genetic diseases that can be passed on through generations.

In Russia, such a biochemical test is one of the mandatory tests during the second trimester. However, it is performed on a voluntary basis. Doctors recommend the test as an additional insurance to obtain information about the condition of the mother and her child.

Possible risks

Any procedure for interfering with the current functioning of the body carries certain dangers. In reality, the risks of medical tests are minimized.

The first screening slightly increases the likelihood of fetal loss. This is the biggest risk associated with this type of analysis. Standard screening will not harm the fetus in any way. However, its perinatal varieties, such as chorionic villus biopsy and amniocentesis, can significantly aggravate the course of pregnancy. In the first case, tissue from the placenta is taken for testing. She will be tested for chromosomes. The risk of fetal loss with this procedure is about 0.9%. As for amniocentesis, during it a thin needle is inserted into the abdomen to obtain amniotic fluid. This procedure can harm the embryo only due to a doctor's error. The risk varies within 0.5%.

It would not be amiss to identify categories of women who need primary and repeat screening. These groups may have a high risk of having a child with gene pathology. These categories of factors include:

Age above 30 years, if pregnancy is the first;
- presence of serious genetic abnormalities;
- with two or more abortions;
- chronic infectious diseases;
- hereditary pathologies in parents;
- marriage with blood relatives;
- any radioactive exposure of one of the parents before or after conception.

Factors influencing the test

Biochemical screening may depend on a number of things. This applies to analysis in both the first and second trimester. Such factors must be taken into account in the final risk assessment. The most common cause of analysis error is maternal overweight. If she is obese, her blood counts will certainly be elevated. If a woman is significantly underweight, then the results will be underestimated.

Multiple pregnancy is also a factor in screening rejection. It is even theoretically impossible to calculate any risk here. The indicators will be elevated, but this is not always considered a genetic disorder. The fact is that in this case the test results are distributed over two or more embryos. Therefore, even repeated indicators will not lead to a clear picture of what is happening.

Bad habits can affect the analysis. This is especially true for smoking. Also, a failure can be recorded if a pregnant woman has a cold during the screening. It is worth noting that this type of analysis is prohibited for diabetes mellitus, as it always gives false results.

Preparing for screening

Diagnosis of the body during pregnancy should always be approached seriously and thoroughly. However, preparation for testing is considered an equally important step, especially if this is the first blood screening. This analysis identifies special markers that indicate the presence of chromosomal diseases. That is why it is important to do everything to eliminate even the slightest possibility of a false rejection.

Firstly, the day before testing, it is prohibited to consume foods such as smoked meats, citrus fruits, chocolate, fried foods, fatty and spicy foods. Otherwise, instead of blood serum, fatty elements are formed in the body. During the centrifugation procedure, it will be almost impossible to separate important cells. In any case, this will significantly complicate the test, and there will be a need to repeat it, which can negatively affect the fetus.

The analysis should always be done on an empty stomach. You are allowed to drink some still water 4-5 hours before the test.

Screening during the 1st trimester

The most suitable period for conducting a primary biochemical test is considered to be 10-13 weeks. It is not recommended to do screening at earlier stages. The price of such an analysis varies from 1800 to 2000 rubles. Based on the results of the initial test, specialists evaluate the health and development of the fetus, as well as the condition of the mother.

Screening during the 1st trimester allows you to identify pathologies such as Down and Edwards syndromes, neural tube defects, heart defects, etc. Before assessing the results, the doctor should always rely on personal examination data, such as blood pressure, temperature, maternal weight, etc. auxiliary factors. In parallel with screening, urine and blood tests are taken for infections. Confirmation of risks is done on the basis of ultrasound.

Screening during the 2nd trimester

Biochemical testing is carried out from 15 to 20 weeks of pregnancy. Doctors do not recommend screening at the end of the trimester. The price of this procedure is about 3,000 rubles. It includes several tests at once. First, chromosomal abnormalities are detected. Secondly, damage to the embryo’s body is detected, in particular in the abdominal cavity and spine. The analysis also allows us to predict the development of Down syndrome in the fetus.

Closer to week 20, the embryo is already quite large. Therefore, it is possible to take a sample of amniotic fluid with minimal risk. This type of screening is called amniocentesis. It is contraindicated to do it if the uterus is toned.

During the 2nd trimester, the most important types of research are ultrasound and biochemical screening.

Decoding and norms of indicators (1st trimester)

Perinatal diagnosis in the first weeks of pregnancy consists of determining several important blood and gene characteristics. The most significant of them are human chorionic gonadotropin (abbreviated as hCG) and PAPP protein. These are extremely important hormones on which the course of pregnancy directly depends.

From 10 to 12 weeks, the normal hCG level is considered to be from 20 to 95 thousand mU/ml. Deviations of 1-2 thousand units are allowed. The normal hCG level at week 13 is 15-60 thousand honey/ml.

PPAP protein in the last month of the 1st trimester should be in the range from 0.3 to 6 mU/ml. At weeks 10 and 11, normal values ​​range from 0.32 to 3.73 units. By the end of the trimester, the protein level should increase to 0.71-6.01 mU/ml.

To exclude deviations due to the age and weight of the pregnant woman, the MoM coefficient is used. Using this medial indicator, it is easier to decipher the biochemical screening of the 1st trimester. Here, the acceptable range is 0.5-2.5 units.

Decoding and norms of indicators (2nd trimester)

Biochemical screening of the 2nd trimester consists of blood characteristics such as hCG, alpha-fetoprotein (AFP) and free estriol (E3). All these are the most important hormones that provide a detailed picture of fetal development.

Biochemical screening standards for the 2nd trimester for AFP are from 15 to 95 U/ml. By the end of the period, the levels may increase to 125. The hCG level in the first half of the trimester should be from 8 to 58 thousand mU/ml. By the end of the period, the figures drop significantly - from 1.6 to 49 thousand units.

Free estriol should be between 5.4 and 28 nmol/l. At the beginning of the period, the maximum threshold is 21 units. By the end of the trimester, the minimum acceptable levels are 7.5 nmol/l.

If the final result of the analysis is presented as a ratio, then the norm is considered to be a risk of less than 1:380.

Reasons for hCG deviation

The results of biochemical screening do not always provide 100% confidence in the presence or absence of a genetic abnormality. Minor deviations from the norm can occur due to a number of reasons. However, you should not pay attention to them if all other tests are in order.

On the other hand, a significant increase in hCG levels indicates trophoblastic disease in the mother, as well as multiple pregnancy. Decreased rates may be a consequence of ectopic fetal development. If fears are confirmed by ultrasound, then the risk of a genetic disease becomes real.

Deviations of other indicators

A highly elevated PPAP level indicates a possible imminent miscarriage or infection. Low protein means the development of Down or Edwards syndrome.

Elevated AFP levels increase the risk of central nervous system defects, umbilical hernia, and liver necrosis. If the level of this hormone is greatly reduced, there is a possibility of premature death of the fetus. AFP can also signal Down syndrome.

Deviation of free estriol from the norm indicates a threat of premature birth, fetal anencephaly, placental insufficiency, and liver disease in the mother.

Prenatal or 1st trimester screening – what is this procedure? How does it work and what does it show? These questions are often asked by expectant mothers on the eve of the examination.

Screening is just a diagnosis that is carried out to identify possible pathologies, disorders and genetic abnormalities in the intrauterine development of a child. The deadline for scheduling the procedure is no earlier than 11 weeks. It is mandatory to take it up to 13 weeks and 6 subsequent permissible days during pregnancy:

• the age of the expectant mother is more than 35 years;
• cases of fetal death;
• miscarriages;
• infectious and inflammatory diseases;
• possible genetic risk of complications, existing pathologies of the previous fetus;
• family ties between parents;
• presence of cases of alcoholism, drug addiction, smoking in the family;
• work in hazardous production;
• taking illegal drugs.

The very first screening is carried out in accordance with the resolution of the Ministry of Health. The gynecologist decides which week it should be done. Usually no later than 13 expected weeks. The prescribed screening for the 1st trimester includes an ultrasound scan, blood testing, and a thorough biochemical analysis of its composition.

Diagnosis at the first ultrasound

Usually performed when fertilization is suspected. Already from the second week of delay of the expected menstruation, an ultrasound examination shows the presence of pregnancy, the approximate timing of the fetus, its development and possible diseases or disorders. It passes abdominally, that is, the abdominal wall is used for examination, without insertion into the vagina. Preparation required:

• diet. Approximately 3 days before the scheduled examination. You should not eat legumes, cabbage, carbonated drinks, baked goods, or fruits before an ultrasound;
• full bladder. 3 hours before the ultrasound, you should not urinate;
• is carried out strictly on an empty stomach. You should not eat food 4 hours before the diagnosis.

Less commonly, a transvaginal or pelvic ultrasound may be performed. More informative. Diagnosis is carried out by inserting an ultrasound sensor into the vagina. No preparation or special diet is required. Screening indicators during pregnancy in the first weeks:

• location of the uterus. Meaning "anteflexio";
• contours. Must be defined as smooth;
• uterus dimensions: 70mm x 60mm x 40mm. Correspond to length, width, diameter;
• walls. The echogenicity is homogeneous;
• fertilized egg. Diameter up to 5 mm or more depending on the period;
• decidualization of the endometrium. Indicates pregnancy;
• the uterine cavity is homogeneous;
• ovarian sizes. Width, length and thickness correspond to the following values: 25mm x 30mm x 15mm.

This examination is usually part of a regular medical examination. A gynecologist cannot always determine pregnancy on his own. If the pregnancy test shows a positive result, further diagnosis is carried out in the early stages. An ultrasound cannot be done earlier than 1.5-2 weeks after a missed period.

Ultrasound at 12 weeks

Prescribed by a gynecologist. It is carried out within the clinic by specialists from 11 to 13 weeks. To determine pathologies and disorders of fetal development and pregnancy. Preparation required:

• diet. For 3 days, complete exclusion of sweets, chocolate, seafood, fatty foods, legumes and cabbage;
• do not urinate for 2-3 hours before the test. When performing abdominal, external ultrasound.

In a timely manner, an ultrasound scan shows the possible genetic risk of having a sick child. Further study of the problem is necessary. The first weeks of pregnancy are very important. The norm of the following values ​​should be indicated in the results:

• embryo size. Measurements are taken from the head to the tailbone. KTE indicator;
• distance from temple to temple. BPR data;
• thickness, density of the collar space, TVP;
• calculation of heartbeats and their frequency, heart rate.

All future parents dream of finding out the sex of the baby through an ultrasound at 12 weeks. But this cannot be determined with certainty. Errors on the part of doctors are too common. In this case, it is better to perform an ultrasound at 16 weeks of fetal development.

Norm and interpretation of results

Many patients ask which week is the best time to do ultrasound screening. If there is data from a previous ultrasound, exact dates are assigned, which assume 12 weeks of pregnancy. In other cases, the timing is determined by a gynecological examination. The norm and interpretation of the results of the first ultrasound should have the following indicators:

• 10 weeks. KTR 33 - 41 mm. TVP up to 2.2 mm. The nasal bone is visible. Heart rate is 161-179 beats. BPR 14 mm;
• 11 weeks. CTE up to 50 mm. TVP – up to 2.4 mm. The nasal bone is visualized. Heart rate – 153 – 177. BPR 17 mm;
• 12 weeks. CTR up to 59 mm. TVP up to 2.5 mm. The nasal bone is more than 3 mm. Heart rate is 150-174. BPR 20 mm;
• 13 weeks. CTE no more than 73 mm. TVP up to 2.7 mm. Nasal bone more than 3 mm. Heart rate - 147-171. BPR 26 mm.

In addition to these data, the baby’s head circumference, the structure of the brain parts, and the distance from the bones: frontal and occipital are determined. The forearms, pelvic bones and thighs are visible. Sizes of the heart and ventricles. The doctor takes into account amniotic fluid and the thickness of the placenta. Poor ultrasound results are also possible, which indicate a genetic risk of developing a sick fetus and corresponding syndromes:

• Down. The TVP or nuchal fold of skin on the baby’s neck has a width of up to 2.8. It is filled with liquid. In Down syndrome, the fluid is dark in color. The nasal bone is shortened, the distance between the eyes is increased, tachycardia and heart pathologies are observed;
• Edwards. There is bradycardia or a decrease in heart rate in the fetus, there is no nasal bone, only one artery is observed in the umbilical cord, an abdominal hernia;
• Patau. Enlarged bladder, tachycardia, impaired brain formation;
• Turner. The fetus has a rapid, unnatural heartbeat and developmental delay corresponding to 8 weeks of pregnancy;
• Smith-Lemli-Opitz. Hereditary genetic disease. The reason is a violation of cholesterol metabolism. Characterized by mutations, craniofacial anomalies, neurological abnormalities;
• de Lange. A disease for which the genetic risk factor is 25%. The condition is possible mutations in the parents. In the fetus, the false positive rate is 5%;
• Triploidy. Lack of division into the corresponding parts of the brain, holoprosencephaly. Decreased heart rate, bradycardia. Omphalocele or malposition of abdominal organs. Enlargement of the renal pelvis and more than two cysts in the cranial area.

For further examination, blood is drawn from the pregnant woman, as well as samples from the fetus. If at least one of the above violations is found, the pregnancy is terminated. This is why screening is so important. Any deviation from the norm arouses specialist suspicion.

Biochemical screening

This examination must be done immediately after the ultrasound diagnosis. What is this: biochemical screening? When the timing of pregnancy has been identified, all indicators of fetal development are indicated, a biochemical blood test or genetic screening must be performed. How does the preparation go:

• exclusion from the diet of foods that cause allergies. Chocolate, smoked meats, seafood;
• ban on fatty foods;
• carrying out the analysis strictly on an empty stomach. It is forbidden to even drink water.

It is advisable to study the hormonal composition of the blood on the same day as an ultrasound examination. Then the doctor will be able to objectively evaluate the results and data obtained. The norms of the biochemical composition of blood are considered according to three indicators. These values ​​are: human chorionic gonadotropin β-hCG, PAPP-A protein and MoM.

Biochemical screening results: β-hCG data

It appears as a second line when taking a regular pregnancy test at home. HCG levels are ambiguous. If it is elevated in the blood, it is possible that future parents should expect twins. Interpretation of β-hCG results in ng/ml:

• 10 weeks from 25.8 to 181.6;
• 11 weeks from 17.4 to 130.4;
• 12 weeks from 13.4 to 128.5;
• 13 weeks from 14.2 to 114.7.

If beta-hCG is elevated at any stage, the fetus may have Down syndrome and the mother may have diabetes mellitus or toxicosis. A decrease in β-hCG norm warns of a possible pathology such as Edwards syndrome, risk of miscarriage, placental insufficiency or ectopic pregnancy. Until the 12th week, this hormone increases, but within normal limits. After that it goes down.

PAPP-A norm at 12 weeks

A protein, protein-A, which is produced by the placenta during pregnancy. It indicates the normal course of fetal development. If PAPP-A is elevated, a woman may experience miscarriage or miscarriage. A decrease in protein indicates genetic diseases. PAPP-A normal levels in the blood:

• 10-11 weeks. PAPP-A from 0.45 mIU/ml to 3.73 mIU/ml;
• 11-12 weeks. PAPP-A from 0.78 mIU/ml to 4.77 mIU/ml;
• 12-13 weeks. PAPP-A from 1.03 mIU/ml to 6.02 mIU/ml
• 13-14 weeks. PAPP-A from 1.47 mIU/ml to 8.55 mIU/ml.

Low rates are a genetic risk for pathologies. Diseases such as Down syndrome, Edwards syndrome, de Lange syndrome. This test is only valid for up to 14 weeks. In the second trimester it becomes uninformative.

After all the data received, the doctor calculates the coefficient of deviation from the norm, MoM. Typically it ranges from 0.5 to 2.5. If it is exceeded to a value of 3.5, it means there are several embryos. The final type of result can be “positive” for pathology or “negative”. Subsequent examination will take place in the 2nd trimester.

The approximate cost of this procedure depends on the location where it is performed. Prenatal diagnostics will cost 1,600 rubles. The difference between ultrasound and biochemical blood sampling for research should not be more than 5 days. You must have all the information about previous examinations with you.

1st trimester screening: what should diagnostics show?

First screening during pregnancy- a set of examinations aimed at identifying the risk of congenital pathologies of the fetus. The diagnostic test includes an ultrasound and a blood test from a vein. The optimal timing for it coincides with the end of the first trimester of pregnancy.

Prenatal screening shows the risk of pathology in the unborn child, but it cannot say with one hundred percent probability about its presence or absence. Deviations from the norm in its results are an indication for other diagnostic studies, during which specialists will make a final diagnosis.

With the help of 1st trimester screening, the expectant mother can find out about a severe congenital anomaly of the fetus and decide in time to terminate the pregnancy.

Time frame for completing the study

Screening in the first trimester of pregnancy can only be carried out from the first day of the 11th week to the sixth day of the 13th week. Conducting studies at an earlier date is not advisable, since the structures examined on ultrasound are still too small to be observed, and the hormones of the biochemical test have not reached the required concentration.

Carrying out an ultrasound examination at a later stage does not make sense. This phenomenon is due to the fact that after the fetus begins to develop the lymphatic system, the fluid of which interferes with the examination of anatomical structures.

The optimal timing for the first screening corresponds to 11-12 weeks of pregnancy. At this time, biochemical tests have the smallest error, and with the help of ultrasound equipment, the anatomical structures of the unborn child are clearly visible. Also, if developmental defects are detected, a woman can have time to undergo a medical termination of pregnancy in a low-traumatic way.

Indications for ultrasound and blood tests

According to the order of the Ministry of Health of the Russian Federation, 1st trimester screening is recommended for all pregnant women. It helps to identify malformations in the early stages of pregnancy and is absolutely safe for the body of the fetus and the expectant mother. Every pregnant woman has the right to decide whether she will undergo prenatal screening.

Mandatory first screening is recommended for women who are in one of the risk groups:

• age over 40;
• history of spontaneous abortion;
• intrauterine fetal death during previous pregnancies;
• the birth of a child with a history of chromosomal abnormalities;
• previous infectious and inflammatory disease during pregnancy;
• the use of drugs that have a teratogenic (causing congenital anomalies) effect on the fetus during gestation;
• alcohol abuse or drug use during pregnancy;
• burdened hereditary history (presence of congenital anomalies in close relatives);
• presence of blood relationship with the father.

Answers from an obstetrician-gynecologist to basic questions about the first screening:

Goals of the first screening

The main goal of screening in the first trimester is to identify the degree of risk of congenital pathology of the fetus. Using ultrasound equipment, a specialist examines “markers” of genetic diseases. Their presence indicates a high probability of chromosomal abnormalities.

Biochemical screening evaluates the amount of hormones produced by the placenta. It is called "dual" because it consists of a count of hCG and PAPP-A. Their deviation from normal values ​​indicates a high probability of congenital diseases.

Using the studies described, specialists can establish an increased risk of certain chromosomal abnormalities - Edwards syndrome, Patau syndrome, Down syndrome, de Lange syndrome, etc. Their danger lies in the fact that many children die in the first months and years after birth, because their organs have an atypical structure and cannot fully perform their functions. But if the child manages to survive, his mental and physical development will lag far behind his peers.

Attention! Both first screening examinations cannot accurately say whether the fetus has a chromosomal abnormality; these tests only reflect the risk of its presence, therefore, if the results are poor, expectant mothers should not fall into despair - quite often the anxiety turns out to be in vain.

High risk according to the first screening is assessed by the width of the neck fold. Normally, it should not exceed 0.3 centimeters. The greater the deviation from this value, the higher the likelihood of a chromosomal abnormality.

Another marker of Down syndrome is the structure of the nasal bone. A high risk of a chromosomal abnormality is indicated by its absence at any stage of pregnancy. After 12 weeks, doctors measure the length of the nasal bone; normally it should exceed 3 mm. The shorter dimensions of this anatomical structure are a marker of chromosomal pathology.

In addition to chromosomal pathologies, screening helps in diagnosing neural tube defects. This group of diseases is characterized by abnormal formation of the brain or spinal cord, which is rarely compatible with life. Also, an ultrasound examination can reveal anomalies of other organs - absence of limbs, heart laying outside the chest cavity, hernial protrusion of the anterior abdominal wall, etc.

Preparing for the first screening

Ultrasound screening can be performed in two ways. The first of them is transvaginal - when the sensor is inserted into the vagina. With this type of ultrasound examination, a woman does not require special preparation.

The second way to conduct an ultrasound is transabdominal - when the sensor is located on the surface of the abdomen. In this case, for reliable results, the bladder must be full, so preparation for the first screening includes taking one liter of fluid an hour before the test.

To undergo the second stage of screening, in the last weeks of the 1st trimester, the expectant mother should donate blood from a vein. Material for biochemical research is collected in the morning. For reliable results a woman should not eat breakfast before the test. On the day of blood donation, only one glass of clean still water is allowed.

Three days before taking blood for biochemical analysis, a woman is recommended to exclude allergens from her diet. These include seafood, peanuts, milk, fish, chocolate. It is also undesirable to eat fried, salted, smoked foods - these foods can distort the results of the study.

To obtain reliable results, a woman should try to relax, since increased activity of the nervous system can affect the production of placental hormones. Before examinations, you should get a good night's sleep and rest. Also many experts recommend excluding sexual activity three days before the proposed screening.

Features of the event

Typically, screening in the first trimester is carried out in three stages. The first of them - preparatory - includes a survey of complaints and an examination by an obstetrician-gynecologist. The specialist collects the woman’s life and hereditary history and calculates the date of conception. For the reliability of screening results, the doctor must know the exact age of the patient, her chronic diseases, endocrine pathologies, and the presence of IVF.

Without fail, the doctor finds out whether there are hereditary diseases in the family. The specialist will also learn about the course of previous pregnancies - the presence of miscarriages, the birth of a child with congenital anomalies, etc. Expectant mothers with a family history are recommended to undergo genetic screening.

After consulting a doctor, the woman is given a referral for an ultrasound examination and biochemical analysis. The order of their implementation differs in different clinics.

Sometimes both tests are done on the same day. This most often happens if the ultrasound is done transvaginally, since you need to drink a large amount of water before a transabdominal ultrasound examination. This may skew the results of the first screening for placental hormones.

Sometimes the study is carried out in two stages. On the first day, the woman undergoes an ultrasound, which calculates the date of conception. The obtained values ​​are necessary to decipher the results of the biochemical test, since the amount of hormones changes every day.

Less often, women first donate blood for a biochemical test. With the results obtained, the expectant mother goes for an ultrasound, where the gestational age is calculated again.

Ultrasound screening

Typically, an ultrasound scan of the fetus does not exceed 30 minutes. If the test is performed transvaginally, a disposable condom is placed over the sensor and then inserted into the vagina. If performed correctly, a pregnant woman should not experience discomfort.

During transabdominal ultrasound, the anterior wall of the expectant mother's abdomen is lubricated with a special gel. The sensor of the device will slide over it, the image is shown on the monitor. Such a study also does not cause discomfort in the pregnant woman.

Many women ask to determine the sex of the child at the first screening. Some doctors may try to look at the fetal pelvic area. However, for accurate results, the baby should be facing the anterior uterine wall.

The longer the pregnancy, the higher the likelihood of correctly determining the sex of the child. At week 11, the number of successful attempts does not exceed 50%. At the end of the 13th week, in 80% of cases, the doctor can determine the sex of the baby.

To carry out ultrasound screening, certain conditions must be met. The first of them is the length of the fetus from the coccyx to the crown of the head is at least 4.5 centimeters. Secondly, the unborn child must take the desired position in the uterine cavity. To do this, the doctor may ask the woman to move around or cough.

During an ultrasound examination, the doctor evaluates the following basic parameters:

• KTR - length of the fetus from the end of the spine to the crown;
• skull circumference;
• BPR - length of the space between the parietal tuberosities;
• TVP - thickness of the collar space (neck fold);
• pulse;
• length of limb bones;
• presence, position, structure of internal organs;
• anatomical structure of the placenta;
• the presence and structure of the nasal bone.

First screening standards:

Gestational age

Nasal bone, mm

Pulse, beats/min

If indicated or at the request of the pregnant woman, the doctor can conduct additional research using a Doppler sensor. This test shows the state of blood exchange between the vessels of the uterus and placenta; pathologies indicate oxygen starvation of the fetus. Also, Doppler ultrasound allows you to see the number of vessels in the umbilical cord - normally there should be two arteries and one vein.

Biochemical screening

To assess the amount of hormones produced by the placenta, specialists draw blood from a vein. This procedure is practically painless; if you are afraid, you should not look at the syringe. First, the laboratory assistant applies a tourniquet to the shoulder, then the woman needs to clench her fist several times. After the described manipulations, the specialist inserts a needle into the vein and takes a few milliliters of blood.

Screening evaluates the amount of human chorionic gonadotropin. This hormone is produced by the placenta, its amount in the blood increases until the 11th week, then it decreases slightly. Many chromosomal and placental abnormalities are accompanied by changes in the amount of hCG.

Screening examinations help identify the risk of chromosomal diseases in a child before birth. In the first trimester of pregnancy, an ultrasound and biochemical blood test for hCG and PAPP-A are performed. Changes in these indicators may indicate an increased risk of Down syndrome in the unborn child. Let's see what the results of these tests mean.

For what period?

Screening of the 1st trimester is done for a period of up to 6 days (the period is calculated from the first day of the last menstruation).

Signs of Down syndrome on ultrasound

The coccygeal-parietal size (CPR) must be at least 45 mm.

If the position of the baby in the uterus does not allow you to adequately assess TVP, then the doctor will ask you to move, cough, or lightly tap on the stomach so that the baby changes position. Or the doctor may advise you to come for an ultrasound a little later.

The measurement of TVP can be carried out using ultrasound through the skin of the abdomen, or through the vagina (this depends on the position of the child).

Although the thickness of the nuchal translucency is the most important parameter in assessing the risk of Down syndrome, the doctor also takes into account other possible signs of abnormalities in the fetus:

The nasal bone is normally detected in a healthy fetus after pregnancy, but is absent in approximately 60-70% of cases if the child has Down syndrome. However, in 2% of healthy children, the nasal bone may not be detected on ultrasound.

The blood flow in the ductus venosus (Arantius) should have a certain appearance, which is considered normal. In 80% of children with Down syndrome, blood flow in the Arancia duct is impaired. However, 5% of healthy children may also exhibit such abnormalities.

Reduced maxillary bone size may indicate an increased risk of Down syndrome.

An increase in bladder size occurs in children with Down syndrome. If the bladder is not visible on an ultrasound scan, then this is not scary (this happens in 20% of pregnant women at this stage). But if the bladder is not noticeable, then the doctor may advise you to return for a repeat ultrasound in a week. At term, in all healthy fetuses, the bladder becomes noticeable.

A rapid heartbeat (tachycardia) in the fetus may also indicate an increased risk of Down syndrome.

The presence of only one umbilical artery (instead of two normally) increases the risk of not only Down syndrome, but also other chromosomal diseases (etc.)

Norm of hCG and free β-hCG subunit (β-hCG)

HCG and free β (beta) subunit of hCG are two different indicators, each of which can be used as a screen for Down syndrome and other diseases. Measuring the free β-subunit of hCG can more accurately determine the risk of Down syndrome in an unborn child than measuring total hCG.

The norms for hCG depending on the length of pregnancy in weeks are possible.

Norms for the free β-subunit of hCG in the first trimester:

9 weeks: 23.6 – 193.1 ng/ml, or 0.5 – 2 MoM

10 weeks: 25.8 – 181.6 ng/ml, or 0.5 – 2 MoM

11 weeks: 17.4 – 130.4 ng/ml, or 0.5 – 2 MoM

12 weeks: 13.4 – 128.5 ng/ml, or 0.5 – 2 MoM

13 weeks: 14.2 – 114.7 ng/ml, or 0.5 – 2 MoM

Attention! Norms in ng/ml may vary between laboratories, so the data provided is not final, and you should always consult your doctor. If the result is indicated in the MoM, then the standards are the same for all laboratories and for all analyses: from 0.5 to 2 MoM.

What if the HCG is not normal?

If the free β-subunit of hCG is higher than normal for your gestational age, or exceeds 2 MoM, then the baby is at increased risk.

If the free β-subunit of hCG is below normal for your stage of pregnancy, or less than 0.5 MoM, then the baby is at increased risk.

Norm PAPP-A

PAPP-A, or “pregnancy-associated plasma protein A” as it is called, is the second indicator used in the biochemical screening of the first trimester. The level of this protein constantly increases during pregnancy, and deviations in the level may indicate various diseases in the unborn child.

The norm for PAPP-A depending on the stage of pregnancy:

8-9 weeks: 0.17 – 1.54 mU/ml, or from 0.5 to 2 MoM

9-10 weeks: 0.32 – 2.42 mU/ml, or from 0.5 to 2 MoM

10-11 weeks: 0.46 – 3.73 mU/ml, or from 0.5 to 2 MoM

11-12 weeks: 0.79 – 4.76 mU/ml, or from 0.5 to 2 MoM

12-13 weeks: 1.03 – 6.01 mU/ml, or from 0.5 to 2 MoM

13-14 weeks: 1.47 – 8.54 mU/ml, or from 0.5 to 2 MoM

Attention! The norms in mIU/ml may vary between laboratories, so the data provided is not final, and you should always consult your doctor. If the result is indicated in the MoM, then the standards are the same for all laboratories and for all analyses: from 0.5 to 2 MoM.

What if PAPP-A is abnormal?

If PAPP-A is below normal for your gestational age, or is less than 0.5 MoM, then the baby has an increased risk of and.

If PAPP-A is higher than normal for your gestational age, or exceeds 2 MoM, but other screening indicators are normal, then there is no cause for concern. Studies have shown that in the group of women with elevated levels of PAPP-A during pregnancy, the risk of diseases in the fetus or pregnancy complications is no higher than in other women with normal PAPP-A.

What is risk and how is it calculated?

As you may have already noticed, each of the biochemical screening indicators (hCG and PAPP-A) can be measured in MoM. MoM is a special value that shows how much the obtained analysis result differs from the average result for a given stage of pregnancy.

But still, hCG and PAPP-A are affected not only by the duration of pregnancy, but also by your age, weight, whether you smoke, what diseases you have, and some other factors. That is why, in order to obtain more accurate screening results, all of its data are entered into a computer program that calculates the risk of diseases in a child individually for you, taking into account all your characteristics.

Important: to correctly calculate the risk, it is necessary that all tests are taken in the same laboratory in which the risk is calculated. The risk calculation program is configured for specific parameters, individual for each laboratory. Therefore, if you want to double-check your screening results in another laboratory, you will need to take all the tests again.

The program gives the result in the form of a fraction, for example: 1:10, 1:250, 1:1000 and the like. The fraction should be understood as follows:

For example, the risk is 1:300. This means that out of 300 pregnancies with indicators like yours, one child will be born with Down syndrome and 299 healthy children.

Depending on the resulting fraction, the laboratory issues one of the following conclusions:

The test is positive – there is a high risk of Down syndrome in the child. This means that you need a more thorough examination to clarify the diagnosis. You may be recommended or.

The test is negative – the child has a low risk of Down syndrome. You will need to undergo, but additional examinations are not needed.

What should I do if I am at high risk?

If, as a result of screening, you have been found to have a high risk of having a child with Down syndrome, then this is not a reason to panic, much less terminate the pregnancy. You will be referred for a consultation with a geneticist, who will once again look at the results of all examinations and, if necessary, recommend undergoing examinations: chorionic villus sampling or amniocentesis.

How to confirm or refute screening results?

If you think that the screening was carried out incorrectly for you, then you can repeat the examination in another clinic, but for this you will need to retake all the tests and undergo an ultrasound. This will be possible only if the gestational age at this moment does not exceed 6 days.

The doctor says I need to have an abortion. What to do?

Unfortunately, there are situations when a doctor persistently recommends or even forces an abortion based on screening results. Remember: no doctor has the right to do such actions. Screening is not a definitive method for diagnosing Down syndrome and, based solely on poor results, there is no need to terminate the pregnancy.

Tell them that you want to consult with a geneticist and undergo diagnostic procedures to identify Down syndrome (or another disease): chorionic villus sampling (if your pregnancy is -) or amniocentesis (if your pregnancy is -).