Biochemical screening of the 1st trimester: what kind of analysis is it, how is it done and why?

In the early stages, when registering pregnant women, they are sent for a mass of tests: KLA, OAM,.

But that's not all. One of the main studies in the first trimester is biochemical screening. What kind of analysis is this, how it is done, the preparation and interpretation of the result will be discussed in the article.

• What is screening
• What is prenatal screening and its purposes
• Prevention of malformations
• Training
• How to pass the analysis
• When will the results be ready
• Why do you need to do an ultrasound
• Timing of prenatal tests
• Pregnant at risk - what to do next
• False positive and false negative results
• How are the tests for chromosomal abnormalities calculated?
• Typical MoM profiles for the 1st trimester
• Typical MoM profiles for the 2nd trimester
• Factors affecting the concentration of biochemical markers
• conclusions

What is screening?

The concept of screening in medicine is widely used. This is a routine study aimed at identifying a risk group for a disease or pathology. There is screening for:

• breast cancer;
• tuberculosis;
• gastrointestinal tumors, etc.

Note! The result of the test is not a diagnosis, but the identification of a risk group.

Why do biochemical screening for pregnant women

During pregnancy, especially in the early stages, it is important to understand which way gestation will develop and whether the fetus will develop at all.

Biochemical screening of the 1st trimester, to some extent, determines the fate. The causes are genetic diseases, chromosomal abnormalities leading to malformations. And according to WHO, 5% of them worldwide. This is natural selection - non-viable fetuses are eliminated from the mother's body.

Nature is not always able to protect a woman from pregnancy with a fetus with genetic disorders. If chromosomal diseases incompatible with life are detected, the “doomed conception” is recommended to be interrupted. At the beginning of pregnancy, it is easier to do this and there are fewer complications for the mother's body. The second purpose of the triple test is to identify the risk of pregnancy complications. The third is to determine the group of pregnant women who will be recommended additional studies if fetal pathology is suspected.

The entire prenatal screening funnel looks like this:

Genetic abnormalities of the fetus can be in a pregnant woman of any age. But the older the woman, the higher the likelihood of their occurrence. This trend is most pronounced for Down syndrome. For other genetic diseases, it is less pronounced, but still present.

Prevention of malformations

In modern medicine, a clear plan has been developed for the prevention and timely detection of malformations. It is necessary to identify malformations incompatible with life and early planned termination of pregnancy.

Not all vices are related to vitality. There are developmental disorders that can be treated immediately after birth, and for some there is the possibility of intrauterine treatment. In such cases, timely assistance saves the lives of newborns. This is also important for situations where the baby needs help in the first hours or 1-2 days after birth. Such pregnant women should choose a maternity hospital in advance, in which they can perform life-saving surgery immediately after childbirth, for example, with aplasia of the esophagus.

Types of prevention:

• preconception;
• perinatal diagnosis.

Preconception prevention is a set of measures aimed at providing optimal conditions for:

• maturation of germ cells in men and women;
• fertilization;
• zygote formation;
• implantation and early fetal development.

This includes healthy family planning, reception, smoking cessation, etc.

When there are chromosomal diseases in the fetus, the concentration and ratio of these substances changes.

Chromosomal diseases are hereditary pathologies caused by changes in the number or structure of chromosomes. They appear during the maturation of germ cells, in the process of fertilization, at an early embryonic stage of development.

A blood test for fetal malformations by itself does not say anything. To decipher and interpret the results, ultrasound data are needed. Due to the fact that it is necessary to conduct 2 studies, biochemical screening is called a double test.

How to prepare for analysis

Special training is not required. A light breakfast, lunch or dinner is acceptable (depending on what time the woman will take the test). The main restriction is a strict ban on fatty foods. Foods with a high fat content will not change the results of the analysis, but will make it difficult for the laboratory technician to work. Since hormone proteins are not determined in the blood itself, but in the serum.

On the appointed day, the pregnant woman comes to the treatment room and, together with the specialist, fills out a detailed questionnaire.

Important! It is necessary to accurately fill out the questionnaire, the data from it is necessary to adjust the risks obtained during biochemical screening.

How the analysis is given - biochemical screening of the 1st trimester

After filling out the questionnaire, you need to weigh yourself. Height and weight must be recorded at the time of blood donation. These parameters are taken into account to adjust the calculated risks during the test.

Blood is taken from the vein of the elbow in a volume of 4-5 ml. Pour from the syringe into a test tube and centrifuge. And then they work not with blood, but with plasma.

How long will the result be

The timing of the analysis varies depending on the urgency. The result can be ready on the same day or within a week.

Why do ultrasound for biochemical screening

Among experts, biochemical screening is called a triple test, because not only hCG and PAPP-A values ​​\u200b\u200bare needed, but also results to determine genetic risks. Namely: the exact gestational age, the size of the TVP (thickness of the collar space of the fetus) and DNA (the length of the nasal bone of the fetus). DNA and TVP are ultrasound markers of malformations, in case of deviation from the norm. The rules for different periods are different.

It's important to know! If the nasal bone is not visualized, the risk of fetal pathologies rises to 47%.

Biochemical indicators and ultrasound markers are necessary for correct calculations of the risks of chromosomal diseases.

The thickness of the collar space is the area in the neck between the skin and soft tissues in which fluid accumulates. A pronounced excess of the norm may indicate abnormalities in the development of the fetus.

TVP norm. Table 1.

Ultrasound is highly accurate and is recommended by an expert class sonologist. The term of the first ultrasound is 11-14 weeks.

Important! The optimal time for an ultrasound as part of a triple test is -.

Prenatal biochemical screening and timing

In obstetrics, there are concepts: biochemical screening of the 1st trimester and biochemical screening of the 2nd trimester. It will not be possible to fully carry out prenatal diagnosis only in the second trimester, since the indicators obtained in the first trimester are involved in the calculations and decoding.

Biochemical screening in the 1st trimester is carried out in the period from 10 weeks of pregnancy to and 6 days. Optimal time - -.

Biochemical screening of the 2nd trimester is done at the term -. Optimal time - -.

A woman at risk - what to do next

The first screening serves to identify risk groups for chromosomal and non-chromosomal abnormalities. In the 1st trimester, risks are assessed for Down syndrome, Edwards, Patau and other genetic diseases that are less common. The risk of developing neural tube defects is not assessed (this occurs during biochemical screening conducted in the 2nd trimester).

The first analysis makes it possible to check the probability:

• development;

These complications of gestation are laid in the first 3-4 months, appear in the 3rd trimester, which allows for early prevention.

If a woman receives a biochemical screening result and the results show high risks for a particular disease, she is recommended to undergo fairly serious studies at prenatal diagnostic centers.

In perinatal centers, it may be necessary to repeat biochemical screening, ultrasound. After that, the question of conducting invasive diagnostics becomes. For a period of 11-13 weeks - this is a biopsy of the chorionic villi.

The chromosome set of the chorion corresponds to the set of the child's genetic material. During the biopsy, pieces of chorion tissue (the future placenta) are obtained for genetic analysis. The probability of error with invasive methods is low, they give an almost 100% accurate answer.

Initially, the tasks of biochemical screening in the 2nd trimester (quadruple test) are the same as in the 1st trimester.

This detection:

• chromosomal abnormalities;
• deviations not associated with genetic disorders that relate to the fetus itself and the course of gestation.

The diagnostic significance of the quadruple test is the definition of malformations. Recommended time frame - - . For biochemical screening of the 2nd trimester (fourth test), the following indicators are examined:

• alpha-fetoprotein AFP;
• free estriol;
• inhibin A.

In the second trimester, the fetus begins to synthesize its own proteins - ACE and estriol. Their number and ratio "characterize" its development.

The results of the 1st trimester screening are required for the second biochemical screening. For calculations, ultrasound data taken at 10-13 weeks are required. The significance of the thickness of the collar space and the length of the nasal bone of the fetus, determined after this period, disappears.

If risks are identified in the 2nd trimester, a woman is sent to a perinatal center, where the need for invasive diagnostics will be weighed:

• amniocentesis;
• cordocentesis.

The significance of amniocentesis and cordocentesis is approximately the same, the choice will depend on which technique is used in the hospital. The probability of complications in invasive diagnostics is 1-2%.

Can there be false positives and false negatives?

Reasons for false results may include:

• incorrectly determined terms of pregnancy;
• accounting results;
• non-compliance with the terms of ultrasound and analysis of biochemical screening;
• incorrect measurement of TVP.

The accuracy of the test is 93%.

The main stages of risk calculations during biochemical screenings

In the analytical laboratory, the following steps take place before the results are issued:

1. Determination of the concentration of analytes (determined substances).
2. Determination of the degree of deviation from the median for a certain gestational age - MoM.

1. Correction of IOM taking into account height, weight, ethnicity, concomitant diseases, results of the previous screening (2nd trimester).
2. Adjustment for age, body weight, risk factors (, bad habits).

Typical IOM profiles in the 1st trimester

What does an increased level of alpha-fetoprotein in the 1st and 2nd trimesters mean?

Typical IOM profiles in the 2nd trimester

Factors affecting the level of a biochemical marker

The decrease in biochemical markers is affected by:

• gestational age (the concentration of analytes varies depending on the period);
• weight (the greater the body weight, the lower the concentration of hormones in the blood);
• ethnicity (levels vary by race);
• twin pregnancy: the concentration of markers is increased, sometimes by 2 times;
• insulin-dependent diabetes mellitus (levels are reduced);
• smoking (hCG levels decrease by 18%);
• pathology of the placenta and its location;
• features of the course of pregnancy;
• pregnancy.

conclusions

Biochemical screenings are important studies required for all pregnant women. They allow you to determine the risks of fetal pathologies and the course of pregnancy, which makes it possible to correct adverse situations for the health of the expectant mother and baby. Most women get good results, which inspires confidence in a happy and healthy future for the child.

Actual video

Prenatal screening

Every pregnant woman at a certain stage of bearing a baby is faced with such a concept as screening. What it is? Screening is a comprehensive examination that gives an idea of ​​the health and development of the fetus, and also allows you to determine the likelihood of a child being born with congenital malformations. Such examinations are carried out every trimester, respectively, three trimesters of pregnancy involve the passage of three screenings.

The first screening during pregnancy makes it possible to identify among expectant mothers those who are at risk of having a child with chromosomal abnormalities and hereditary diseases. Every pregnant woman should read the information: what is included in the screening of the 1st trimester, for how long it is usually carried out, what are the standards for screening of the 1st trimester and what to do if the examinations show poor results.

Timing and indications for the first screening

First trimester screening can be considered reliable if performed between weeks 11 and 14. It will be optimal to do screening at 12 weeks of pregnancy. It is for this reason that it is very important to register for pregnancy before this date. The best time to perform a 1st trimester screening should be determined by the gynecologist who manages the woman's pregnancy. It is still not too late to do screening at 13 weeks of gestation, but its results will still be less reliable. It is also worth noting that perinatal screening performed in the first trimester of pregnancy will be more informative than screening in the second trimester.

1 pregnancy screening is not mandatory, but medical professionals advise not to neglect this examination if a woman wants to be well aware of the health status of her unborn child. Among pregnant women, there are certain risk groups. If a woman belongs to one of these groups, then the doctor will strongly recommend that she undergo 1st trimester screening:

• the pregnant woman had two or more spontaneous abortions (preterm birth);
• the woman experienced a missed pregnancy or stillbirth;
• during pregnancy, the expectant mother suffered a viral or bacterial disease;
• among family members there are people with genetic pathologies;
• the woman already has a child with chromosomal abnormalities or severe genetic diseases;
• the woman was treated with drugs that are prohibited for pregnant women;
• the age of the woman is more than 35 years;
• the father of the child is a blood relative of the pregnant woman.

The first pregnancy screening is quite informative in terms of identifying the following pathologies:

• anomalies of the neural tube (rudiment of the central nervous system);
• Smith-Opitz syndrome;
• Cornelia de Lange syndrome;
• omphalocele (umbilical hernia, manifested by the fact that some of the internal organs of the fetus are not in the abdominal cavity, but in a hernial sac that emerges on top of the skin).

Each pregnancy is individual, which means that screening for different women can take place in different ways. It will be enough for someone to pass the necessary tests once and no longer worry throughout the pregnancy. Others are prescribed the same examinations several times. It is worth noting that negative results are not yet a reason for panic. You need to take them as a signal that more careful monitoring of the course of pregnancy is required.

How is first trimester screening done? This examination includes an ultrasound examination (ultrasound) of the fetus and a biochemical analysis of the mother's blood.

first trimester ultrasound

Ultrasound has long been a universal method by which all pregnant women are examined. The technique is simple to perform, informative and does not pose a threat to the health of the mother and fetus. For a long time using the procedure, experts have not found any harm from the effects of ultrasound on the development of the fetus. In obstetrics, two types of ultrasound are used for the 12th week of pregnancy:

• Transvaginal (a specialist inserts an ultrasound probe into the vagina);
• Abdominal (to obtain an image, the sensor is driven along the mother's stomach).

How to prepare for an ultrasound? Special preparation for an ultrasound examination at 12 weeks of gestation is not required. It would be desirable for a pregnant woman to drink about 500-1000 ml of non-carbonated water, since the amount of amniotic fluid during this period of pregnancy is still insignificant, namely, the amniotic fluid makes it possible to examine the fetus as well as possible. Also, a day or two before the examination, it is better to exclude foods that can increase the formation of gases in the intestines. Excess gases can distort diagnostic results.

Up to 10 - 11 weeks of pregnancy, a fertilized egg has an extremely small size - from 2 to 4 mm. The maximum that an ultrasound specialist can detect in the early stages:

• the location of the embryo;
• the umbilical cord of the fetus;
• to fix the presence of the rudiments of the upper and lower extremities;
• determine the presence of the makings of the auricles;
• determine the condition of the woman's uterus.

After 10-11 weeks, the fetus reaches the size necessary for a more detailed diagnosis of intrauterine development. This stage of the formation of the internal organs and systems of the embryo allows specialists to detect certain malformations in development. Some of these pathologies may even be incompatible with life, therefore, avoiding ultrasound at this time would be quite imprudent.

The main goals that ultrasound of the first trimester sets for itself:

• determination of the number of fetuses in the uterus;
• detection of the placenta attachment;
• detection of abnormal conditions of the fetus;
• definition of non-developing pregnancy;
• identification of the threat of spontaneous miscarriage;
• establishing an ectopic pregnancy;
• detection of pathologies in the reproductive organs of a pregnant woman;
• assess the quantity and quality of amniotic fluid;
• determine the occurrence of tumors and cysts.

Diagnosis of a number of diseases during the first ultrasound screening gives doctors the opportunity to provide timely assistance to the expectant mother and child in order to avoid complications during pregnancy.

What do specialists first of all pay attention to when they do an ultrasound - screening of the 1st trimester?

First, the doctor will measure the coccyx-parietal size of the fetus (CTE). This indicator refers to the size of the fetus from the coccyx to the crown of the head, not taking into account the length of the legs. The value of the CTE should correspond to the gestational age. A situation in which the fetus is larger than the norm indicates that the baby is developing rapidly and, most likely, the expectant mother will have to bear and give birth to a large child.

The small size of the CTE may indicate either an incorrectly set deadline, or the following deviations in development:

• genetic abnormalities in the fetus;
• developmental delay due to hormonal deficiency, infections or other diseases of the pregnant woman;

If the doctor fails to listen to the heartbeats of the embryo, then intrauterine death of the fetus is ascertained. Usually it is accompanied by the loss of symptoms of toxicosis. As a result, some expectant mothers worry and wonder why they don’t have toxicosis in the first trimester? However, the absence of nausea and a cheerful state of health at the beginning of pregnancy is a phenomenon, although infrequent, but absolutely normal. The first ultrasound will help such women calm down and understand that everything is in order with the baby.

On ultrasound, the doctor will definitely evaluate the size of the collar space of the fetus. The thickness of the collar space (NTP) during normal development of the embryo should not exceed 3 mm. Too much accumulation of fluid in this zone leads to an increase in TP and may be evidence of the presence of chromosomal abnormalities in the fetus, primarily Down syndrome. It is necessary to measure TVP precisely in the period from 10 to 14 weeks, since then it will be ineffective to study this marker of chromosomal abnormalities. As a rule, doctors are guided by the following norms for the size of TVP, which differ in terms of gestational age:

It should be remembered that the development of each child is an individual process and the deviation of the thickness of the collar zone from the norm is not yet a sentence and does not give grounds to establish any final diagnosis.

Another important indicator for ultrasound is the biparietal size (BDP) of the fetal head. It is measured from temple to temple. This value also changes upwards with each new week of pregnancy. Too large BDP can be due to the following reasons:

• a woman is carrying a large fetus (other sizes will also be above the norm);
• spasmodic growth of the embryo (in a couple of weeks the parameters will even out);
• the fetus has a brain tumor or cerebral hernia (these deviations are incompatible with life);
• hydrocephalus (dropsy) of the brain, which was the result of an infection suffered by the mother (with successful antibiotic treatment, pregnancy can be saved).

Small BDP may indicate underdevelopment of the brain.

On ultrasound of the first trimester, the specialist also notes the presence or absence of the nasal bone in the fetus. The absence of this indicator should alert the doctor, since it is in the presence of chromosomal abnormalities that fetal ossification occurs later.

Ultrasound examination enables obstetrician-gynecologists to identify a risk group among women who are expecting a baby. First of all, this applies to those whose fetal parameters and ultrasound norms do not match. Pregnant women at risk are referred for more thorough examinations to confirm or exclude the possibility of having a child with a hereditary pathology.

Ultrasound - screening at week 12 (as, indeed, during the entire first trimester) rarely allows you to accurately determine the sex of the child. In some medical centers, future parents are offered to record a memorable video with the baby.

Biochemical screening

The second important step that is included in genetic screening during pregnancy is the hormonal (biochemical) assessment. To pass this diagnosis of a pregnant woman, it is enough just to donate blood from a vein. This must be done in the coming days after the ultrasound procedure. Special preparation for the analysis is not needed, but it is advisable to exclude fatty foods from the diet a day before blood sampling, do not smoke 30 minutes before the study and exclude physical and mental overstrain. Pregnant women often ask the question - is it possible to eat before screening? It is best to refrain from eating before blood sampling, as even a light breakfast can distort the results of the analysis.

A general blood test in the first trimester is prescribed for absolutely all pregnant women. What does this analysis show? Firstly, it allows you to identify the presence of diseases, including sexually transmitted ones, which can cause severe fetal pathologies: rubella, viral hepatitis B, chlamydia, etc. The following indicators are also mandatory to be studied:

• Blood glucose level

  This parameter helps to prevent and timely notice the onset of gestational diabetes. Timely prescribed treatment and diet will help to avoid complications during pregnancy and the occurrence of pathologies in the fetus.

• Blood protein level

An increased level of protein in the blood may indicate pathologies of the urinary system and kidneys of the mother, and possibly the development of preeclampsia.

As part of prenatal screening, the concentration of certain hormones, the level of which increases in a woman during pregnancy, is assessed. In the first trimester, the following indicators are evaluated during screening: free b-hCG and plasma protein-A (PAPP-A). What it is?

Human chorionic gonadotropin (hCG) is a hormone that is produced by the placenta during pregnancy and is one of the most important indicators of a favorable pregnancy. Each week of pregnancy corresponds to its own norm of the concentration of hCG in the mother's blood:

If the pregnancy is not multiple, then an increased level of hCG may indicate the following:

• there is a high probability that the fetus has Down syndrome;
• may have a hydatidiform mole or choriocarcinoma (a rare malignancy).

A reduced concentration of b-hCG in the first trimester may indicate the following dangerous conditions:

• Edwards syndrome or Patau syndrome in the fetus;
• ectopic pregnancy;
• placental insufficiency
• the threat of spontaneous abortion;

PAPP-A (pregnancy-associated protein A). This protein is produced by the fetal trophoblast, and its concentration in maternal blood in the early stages increases every week of pregnancy. Clinical studies have long confirmed that PAPP-A levels are an excellent marker for detecting a high risk of chromosomal abnormalities in the fetus, which helps to detect severe diseases already in the early stages of pregnancy. Each week of pregnancy corresponds to its normal level of PAPP-A:

The most dangerous condition is precisely the decrease in PAPP-A relative to the norm. This may indicate the presence of the following deviations:

• the development of one of the chromosomal abnormalities: Down syndrome, Edwards syndrome or Cornelia de Lange syndrome;
• spontaneous miscarriage or intrauterine fetal death.

What does an elevated PAPP-A level show? In general, with normal other indicators, such a deviation should not cause much concern. Pregnant women with elevated PAPP-A levels have not been shown to have a higher risk of fetal malformations and complications during pregnancy than women with normal PAPP-A levels. An increase in the concentration of this hormone can be justified by the following reasons:

• a woman bears several fetuses (twins / triplets);
• the fetus is large, and the mass of the placenta is increased;
• low placenta.

After the 14th week of pregnancy, it is not worth taking an analysis for PAPP-A, as it will be considered non-informative.

When screening for the first trimester, experts consider both indicators (b-hCG and PAPP-A) in combination. In the case when PAPP-A is reduced and b-hCG is simultaneously elevated, the doctor is likely to suspect the presence of Down syndrome in the fetus. A decrease in both markers may indicate the presence of Edwards syndrome or Patau syndrome.

There is a possibility that a blood test may give false values. Reasons for skewed results may include:

• obesity, due to which hormonal levels become unstable;
• fertilization with IVF. PAPP-A will be lower by 10-15%, hCG is increased, and ultrasound will show an increase in the fronto-occipital size of the fetus.
• multiple pregnancy.
• stressful condition of a woman.
• diabetes.

After undergoing an ultrasound procedure and donating blood for biochemical markers, the risk of chromosomal abnormalities in the fetus will be calculated for the expectant mother. The results of the screening of the 1st trimester (ultrasound, the level of biochemical markers in the blood) and the mother's personal data will be entered into a special program. The following is indicated as personal data:

• the age of the pregnant woman;
• date of blood sampling, date of ultrasound and gestational age;
• the number of fruits;
• the mother has type 1 diabetes).
• body weight of the female patient;
• ethnicity of the patient;
• does the woman smoke during pregnancy;
• pregnancy occurred naturally or through the use of assisted reproductive technologies (IVF).

After processing the data, the program gives the risk of gene anomalies in numerical form, for example, 1:1900. This would mean that for every 1900 women with the same screening characteristics, there may be one case of the birth of a sick child. A 1:100 screening result in Russia would be considered a high risk threshold. The complex of all screening studies makes it possible to detect Down syndrome with a certainty of 85%.

Identified high risk of Down syndrome on the first screening is not such a rare occurrence. However, it should be understood that deciphering the results of screening is not a final diagnosis and not a sentence, but only an estimated risk of pathology! If it happens that the screening of the 1st trimester shows disappointing results, then the woman will need to seek professional advice from a geneticist, who will most likely prescribe a more thorough examination for the pregnant woman. It usually consists in the use of invasive diagnostic methods: chorionic villus biopsy (at 10-13 weeks of gestation) or amniocentesis (16-17 weeks of gestation).

Both of these procedures involve surgery and are performed in a hospital. Under the supervision of an ultrasound machine, a specialist punctures the anterior abdominal wall of the mother and collects material containing fetal DNA. In the case of chorionbiopsy, these are pieces of placental tissue, with amniocentesis - amniotic fluid (amniotic fluid). The study of the obtained biomaterials makes it possible to establish with high accuracy (about 99%) the presence or absence of chromosomal abnormalities and congenital diseases in the fetus.

However, these methods have their own significant drawbacks - they are quite unpleasant and stressful for a woman. In addition, there is a risk of spontaneous miscarriage (in about 1.5% of cases) provoked by these procedures. Occasionally, invasive diagnostics lead to a complication of the course of pregnancy, which is expressed in the leakage of amniotic fluid, bleeding, trauma to the fetus, etc.

Modern medicine also offers alternative, safe methods of high-precision prenatal diagnosis. One of these methods is a non-invasive prenatal DNA test based on modern molecular technologies. The test has long been successfully used in medical centers abroad and is becoming increasingly popular among Russian doctors. The test process is as follows:

• a pregnant woman donates blood from a vein;
• fetal DNA is isolated from the obtained material using the sequencing method;
• the genetic material of the fetus is analyzed for the presence of chromosomal pathologies and some hereditary diseases;
• future parents are provided with a detailed transcript of the results of the analysis.

This non-invasive technique has an accuracy of over 99%, which is significantly higher than the accuracy of the combined analysis of screening tests (ultrasound and biochemical blood test). As a result, some modern mothers prefer this test to traditional screening, although it is somewhat more expensive. The advantage of the method is that already at the ninth week of pregnancy it allows to detect a wide range of gene anomalies and hereditary diseases in the fetus. For many expectant mothers, this test allowed them to avoid unsafe invasive diagnostics, and simply helped to gain confidence in the health of their unborn child. In addition, thanks to this method, you can find out the sex of the fetus.

Favorable results of a non-invasive DNA test give an almost 100% guarantee that the fetus does not have the chromosomal abnormalities for which its DNA was tested. If the result indicates a high risk, the woman will still have to undergo an invasive examination, since only the conclusion of an invasive diagnosis can be the basis for an abortion for medical reasons.

In cases of poor results from invasive tests, doctors are likely to recommend that the woman have an abortion for medical reasons. In some cases, such a measure will indeed be justified and reasonable action. However, no one has the right to force a pregnant woman to take such actions; in any case, the decision must be made by the woman herself and her family. It should be understood that any decision in this case must be balanced and well thought out. Many underestimate all the hardships and trials that will have to endure, agreeing to give birth to a baby with severe defects.

Where to do 1st trimester screening?

questions about screening that concern expectant mothers: how is screening done at 12 weeks, where to do screening for the 1st trimester in Moscow, how much does the first ultrasound cost, what is the price in Moscow for biochemical screening, etc. etc.

Naturally, the price for screening of the 1st trimester will differ significantly depending on the city in which the expectant mother lives and how prestigious the medical center she chooses for this examination. It is advisable to contact institutions that specialize in genetic research.

Is 1st trimester screening worth it?

Alas, even the most healthy parents are not immune from the birth of a child with severe defects. The well-known Down syndrome, for example, can occur due to an accidental error during the division of maternal or paternal cells. It is not possible to influence it during pregnancy, since the mechanism for the development of an anomaly starts already at the moment of conception. Many people are also carriers of genetic abnormalities, completely unaware of it. This is revealed only when a sick child is born in the family. Based on at least these two factors, a pregnant woman should not avoid first trimester screening.

Of course, it is worth knowing that many patients are dissatisfied with the quality of screening calculations. Often, in cases of established high screening risk, healthy babies were born, and poor screening results forced a woman (if she refused invasive diagnostics) to be stressed during pregnancy.

There are quite a lot of families that are ready to accept and raise a child, even with severe disabilities. In this case, you can refuse to undergo screening, but first you should soberly weigh your moral and material capabilities, as well as find out as much information as possible about congenital malformations and genetic abnormalities.

If a married couple realizes that it is extremely important for them that the baby is healthy and can lead a full life, then 1st trimester screening should be included in the list of prenatal examinations for a woman. The identified high risk of pathologies will be a reason for more careful monitoring by a gynecologist and a geneticist, and a low risk will allow you to enjoy pregnancy without unnecessary worries.

Biochemical screening during pregnancy - this word refers to the analysis of venous blood, which determines special hormones that are markers of fetal chromosomal pathologies. It is the results of this examination that determine, without being a diagnosis, how high the risk of malformations in a growing fetus is. This is what a biochemical examination is in an “interesting period”, and it should only be carried out in conjunction with an ultrasound examination at the same time.

Do pregnant women need biochemical screening

The study can be carried out for all women who want to be sure that their child will be born healthy (meaning - without a chromosomal pathology that is not treated). But there are also strict indications, given that the gynecologist of the antenatal clinic gives a direction for biochemical screening. These are the following situations:

1. future parents are close relatives
2. this woman has already had a stillbirth or the pregnancy has stopped
3. mother over 35
4. already have 1 child with some kind of chromosomal pathology
5. for a long time there is a threat of spontaneous miscarriage
6. there was a single or repeated case of miscarriage or premature spontaneous labor
7. a pregnant woman suffered a viral or bacterial pathology during or shortly before pregnancy
8. it was necessary to take medications that were not allowed for pregnant women
9. before conception, one of the couple was exposed to ionizing radiation (X-ray, radiation therapy)
10. doubtful results of ultrasound diagnostics regarding malformations.

Perinatal diagnosis for hormone levels is carried out only in conjunction with screening ultrasound during pregnancy.

What pathologies are determined by the study of the blood of pregnant women

These are such diseases:

1. Edwards syndrome
2. neural tube defect
3. down syndrome
4. patau syndrome
5. de Lange syndrome

Syndromes of Edwards, Patau and Down are united by the common name "trisomy". Moreover, each cell does not contain 23 pairs of chromosomes, but 22 normal pairs and 1 "triplets". In which pair the "trinity" was formed, the disease is called.

For example, if screening for Down is performed, then there are three (not two) 13 chromosomes (the syndrome is also written "Trisomy 13"). These conditions must be identified prior to 3rd trimester screening.

Preparation for analysis for chromosomal pathologies

Preparation for the diagnosis of the 1st trimester for markers of chromosomal diseases is that the day before the study you exclude from the diet:

• spicy food
• fatty and fried foods
• smoked meats
• chocolate
• citrus.

When a long-awaited pregnancy comes, a woman tries with all her might to make it as successful as possible. Today, medical diagnostics are a great way to detect malformations and prevent their consequences without harming the mother and child.

Today, there are no expectant mothers who do not undergo the first prenatal screening. This is a comprehensive study that can detect pathologies and anomalies in the development of the fetus in the early stages. It also includes an analysis of the plasma protein PPAP. Every expectant mother should know about the rate of PAPP-A during pregnancy. This indicator plays an important role in diagnosing one form or another of the developmental disorder of the future crumbs.

What is screening for?

A pregnant woman is wary of any examination prescribed by a doctor. After all, now the main thing is that nothing threatens the baby. Therefore, when a gynecologist gives a referral for screening for a period of 13 weeks 6 days, the expectant mother often does not know what to expect from all this and is very worried.

In fact, the prenatal examination is as safe as possible and is assigned to absolutely everyone at 11-13 obstetric weeks due to simple methods of its implementation:

• ultrasound procedure;
• screening biochemical blood test.

The first prenatal screening is scheduled for 11-13 weeks 6 days. It is during this period that this survey is most informative.

It is especially important to undergo a study for a woman with a burdened pregnancy or previous unsuccessful attempts to bear a baby. These risk factors include:

• a woman whose age is 35+;
• the presence of previous pregnancies that ended in spontaneous miscarriages or non-developing pregnancy;
• a child with a chromosomal or genetic pathology is already growing in the family;
• during a real pregnancy in the early stages up to 13 weeks, a serious infectious disease was transferred;
• the impact of harmful factors associated with the woman's profession;
• addiction of the expectant mother to alcohol, drugs.

First of all, an ultrasound examination is performed, and then on the same day blood is donated for biochemical screening. Compliance with this sequence in the aggregate guarantees a reliable result of the study. The first screening requires the most correct gestational age, up to the day. Only a doctor of ultrasound diagnostics can set the exact date. In addition, only an ultrasound will give a result on whether the pregnancy is singleton or multiple. Without this information, it is generally not advisable to donate blood, since you will not receive high-quality results.

Biochemical blood test at screening in the 1st trimester

At the time of blood donation, the expectant mother should already have the results of an ultrasound scan with the exact gestational age and accompanying comments from the doctor. For example, if ultrasound diagnostics revealed fetal fading, then further analysis is simply pointless.

Donating blood for such an examination implies a number of rules:

1. Taken exclusively on an empty stomach. Water is allowed only if the mother has severe toxicosis or dizziness.
2. If possible, donate blood as early as possible, but without confusing the sequence of procedures. If the process of donating the biomaterial is long in coming, take a snack with you and eat immediately after leaving the treatment room.
3. A couple of days before the scheduled study, exclude a number of foods from the diet: fatty and smoked foods, nuts, chocolate, seafood.
4. The day before the delivery of the biomaterial, heavy physical exertion should be excluded.

A blood test for biochemistry is aimed at studying two indicators:

• free human chorionic hormone (hCG);
• plasma protein PAPP-A.

The results of biochemical screening are ready within 2 days.

What is RAR-A

PAPP-A is a plasma protein that the body begins to actively secrete during pregnancy.

It is produced by the outer layer of the embryo at the moment when it is introduced into the walls of the uterus. That is why a blood test for the level of this protein is of paramount importance for the early diagnosis of the abnormal development of an unborn baby. Even at the very beginning of pregnancy, when ultrasound is unable to see the problem, PAPP-A indicators can signal its presence.

A change in the quantitative deviation from the norm of PAPP may indicate:

• Down syndrome;
• frozen pregnancy;
• risk of miscarriage.

A blood test for PAPP-A must be taken before the 14th week of pregnancy. At later dates, reliable results should not be expected. After 14 weeks, the PAPP-A indicator in a woman with a genetic chromosomal pathology of the fetus will be exactly the same as in a woman carrying a healthy baby.

Any deviation from the norm during pregnancy, whether it is an increase or decrease in the level of plasma protein, should be a cause for concern.

IMPORTANT! Only a combination of the results of ultrasound and biochemical screening can give a complete picture of the course of pregnancy. Blood should be donated no later than 3 days after the ultrasound examination. The doctor does not give you an accurate diagnosis, but only indicates possible pathologies that can be confirmed or refuted using more accurate examination methods.

The results of a blood test for PAPP-A

When interpreting the results of the first screening, the gynecologist takes into account all the features of a pregnant woman: weight, the presence of diabetes, whether any medications were taken at the time of the study, the presence or absence of bad habits, the pregnancy was obtained through IVF or not, and many others.

Plasma protein levels rise from 8 to 13-14 weeks.

Normally, in a pregnant woman, the PAPP-A indicator varies depending on the week of pregnancy.

Deviations from the norm may indicate a genetic-chromosomal pathology on the part of the fetus, and a pregnant woman is at risk associated with fetal fading or spontaneous miscarriage.

Pregnancy-associated PAPP-A can also be elevated for a number of other reasons:

• sufficiently large weight of the child;
• low location of the placenta;
• multiple pregnancy.

Analysis results in MoM

When the results of blood screening get to the doctor leading the pregnancy, he converts the indicators in units into the MoM coefficient. It reveals the percentage of deviations in a particular woman from the average norm.

With a positive screening result, the MoM coefficient varies from 0.5 to 2.5.

In all laboratories, the norms of the MoM coefficient are the same. Therefore, to retake the analysis, you can choose absolutely any institution if you do not trust the results of your own.

PAPP-A norms for multiple pregnancy

Already at a period of thirteen weeks during 1 screening, the doctor can detect two or more embryos in the uterine cavity. Multiple pregnancy belongs to a number of complicated ones and requires special control throughout the entire period of bearing babies. The risk of such a pregnancy may be that one fetus develops without visible pathologies, and the second has signs of developmental abnormalities as early as 13 weeks. Therefore, it is very important for the expectant mother to seriously approach the issue of the first prenatal screening.

At 1 screening during pregnancy, the double norm of analyzes will be slightly different than during a singleton pregnancy.

Firstly, the main study will be ultrasound, where the doctor will pay special attention to the collar zone of babies. It is there that fluid accumulates, signaling a possible Down syndrome.

Secondly, a biochemical blood screening will not be prescribed by a doctor. In the case of multiple pregnancy, it will be uninformative and can give both falsely increased and falsely decreased results. It is possible that only the MoM coefficient can be determined from the mother's blood. Normally, in a pregnant twin, it reaches 3.5 MoM.

The first prenatal screening at 13 weeks is an exciting procedure. Any mother should know that no doctor can make an exact 100% diagnosis. Analysis on PAPP-A is the identification of the probability of risk. Only the combination of ultrasound and blood biochemistry results can slightly increase the level of reliability.

Even if a high risk of giving birth to a sick baby is detected, you should not take rash and reckless steps. An obstetrician-gynecologist will advise a consultation with a geneticist and will provide an opportunity for re-screening if the period has not crossed the border of 13 weeks and 6 days.

There is no need to refuse the proposed examinations. Forewarned is forearmed.

Screening of the 1st trimester, what is it and when should it be carried out? Is it mandatory and how accurately are the results interpreted? This examination is a combination of two - ultrasound and blood tests, which must take place on the same day.

Prenatal screening in the 1st trimester is considered reliable if 2 conditions are met.
1. It was performed by an experienced specialist in terms of 11 to 13.6 weeks. In this case, the CTE of the fetus should not be less than 45 mm, otherwise the measurement of TVP (collar space) cannot be considered reliable for calculating the risk of having a child with chromosomal pathologies.

2. Risks should be considered, not relying only on ultrasound data, and not looking only at biochemical screening of the 1st trimester. This work must be performed by a special program. And it will give a result on the risks for various genetic and chromosomal diseases. The risks will be registered as average (where only age is taken into account) and individual. So the screening of the 1st trimester is bad if the individual risks are higher than the base (age). In this case, the doctor may refer you for a consultation with a geneticist. And already he, perhaps, will prescribe as soon as possible to repeat ultrasound, only an expert class and (or) invasive diagnostics (cordocentesis, chorionic villus biopsy or amniocentesis). Recommendations will largely be based on ultrasound data. Sometimes at this time, the doctor of ultrasound diagnostics sees very severe malformations in the fetus that are incompatible with life. In this case, a second ultrasound is prescribed and interruption is recommended. Invasive diagnosis is usually not necessary.

If the ultrasound screening of the 1st trimester is generally normal, but the individual risk of having a sick child is high, then the doctor may recommend waiting for the second screening or conducting an invasive diagnosis, the result of which will tell you exactly whether the child is genetically healthy.

In the early stages, a chorionic villus biopsy is performed - this is a rather risky procedure, in terms of a high risk of miscarriage after it. For genetic analysis, the doctor takes cells from the placenta, this procedure is also called a placental biopsy.

After 16 weeks, amniocentesis is done. Amniotic fluid is taken for analysis. This analysis is considered very informative and safer than chorionic villus biopsy and cordocentesis. Women usually agree to the first one in order to avoid prolonged bearing of a non-viable fetus. After all, after 12-13 weeks, you need to wait for the period when doctors can induce artificial labor. And that's about 18 weeks.

But if you didn’t fall into the norms of screening for the 1st trimester by ultrasound, and you don’t want to wait for the second screening, and even more so for invasive diagnostics, there is an opportunity to do a non-invasive test. While in Russia it is not common. And very expensive. An analysis costs about 30,000 rubles. But its reliability is about the same as amniocentesis. There is no risk of spontaneous abortion.

1st trimester screening involves looking at the levels of two hormones in the blood of the expectant mother - hCG and PAPP-A. High hCG may indicate a high risk of Down syndrome in a child, and low hCG may indicate Edwards syndrome. At the same time, PAPP-A is also low. But the final interpretation of the results of screening of the 1st trimester is performed only together with ultrasound.

The result of blood tests can be affected by a situation where a woman has a clear threat of miscarriage if she takes progesterone preparations. But with the threat flow very many pregnancies. In addition, a woman carries one or several fetuses, whether she has excess or underweight, whether the conception was natural or in vitro fertilization. Therefore, it is completely wrong to try to interpret and worry about separate blood tests.

When it is better to do screening of the first trimester - the gynecologist can and should calculate directly. That is why it is important to register for pregnancy before 12 weeks. It is advisable to come to the doctor for the first time no later than 8-9 weeks, since there is a shortage of coupons for free screening in many Russian regions. You may need to wait a bit to get a coupon. You just have to wait for this extra time.

But the timing of the screening of the 1st trimester has been determined. It remains only to donate blood and do an ultrasound on the specified day. Many women believe that for greater reliability of the result, some measures need to be taken. Should there be preparation for the first screening during pregnancy and what kind? As such, no preparation is needed. Some experts recommend following a diet a few days before the examination, but this is not very necessary. There is no need for a future mother to limit herself in nutrition. And one more important question - how is the first trimester screening done on an empty stomach or not, what is the best way? In general, it is advisable to take all blood tests on an empty stomach. Including this one. But sometimes it happens that the analysis is scheduled for the second half of the day. Then, of course, you should not starve from the evening of the previous day.

An ultrasound is performed. And sometimes the doctor needs not only abdominal access, but also vaginal. Indicators that are of particular interest to the doctor are the thickness of the collar space, the visualization and size of the nasal bone, and the speed of venous blood flow. In addition, the doctor looks at all the organs and systems of the fetus, the size of the limbs, the head. Measures the cervix of a woman in order to diagnose isthmic-cervical insufficiency at an early stage, if any.

The results of the 1st trimester biochemical screening are usually ready within a few days. And all this time, the expectant mother is in suspense. Especially if you read or personally know the bad stories associated with this survey. Usually a woman visits a doctor once every 2-3 weeks, and if a high-risk screening result arrives before she is due to attend an antenatal clinic, the doctor or midwife calls her and invites her to come. If there is a good screening of the first trimester, you don’t have to worry and additionally don’t take anything and don’t visit genetics. It should be noted that young women have a much lower risk of chromosomal abnormalities.

Screening of the 2nd trimester consists in the delivery of three blood parameters. But it is usually prescribed only to those women who either did not pass the first screening, or its results were unsatisfactory.

And in conclusion, it should be said about how much the first screening is generally needed. Is it possible to do without it? Of course, yes, it all depends on the desire of the woman. On ultrasound at 12 weeks, severe malformations can be detected. Well, high or low risk is not a guarantee of the birth of a sick or healthy child.

However, classical screening is recommended to be mandatory for women over 35 years of age and those who already have children with genetic abnormalities, or cases of bearing children with chromosomal abnormalities, if there are deviations in the genetic code.