Interpretation and norms of prenatal screening for the 1st and 2nd trimester


The examination under consideration is carried out in the interval between 16 and 20 weeks of pregnancy, and it consists of two stages: ultrasound and biochemical screening. In the absence of any abnormalities on the ultrasound, a triple test is often not assigned.

In general, screening for the second trimester of pregnancy is a voluntary procedure. In some cases, the results may be false-positive, which provokes stress and adversely affects the health of the mother.

On the other hand, thanks to such diagnostics, it is possible to identify and promptly eliminate the factors interfering with the normal course of pregnancy.

Ultrasound procedure

This type of diagnosis makes it possible to make a complete assessment of the level of fetal development, to confirm or refute the presence of physiological abnormalities.

Due to the age of the baby, the following indicators can be fixed by means of an ultrasound probe:

Gender can be determined if the embryo is located appropriately.

Otherwise, future parents will remain in ignorance until the next screening, or until the birth of the child.

2. Fetometric data of the fetus

Include several components:

  • The length of the humerus and forearm. The doctor checks the presence of all bone tissue, symmetry of the forearms.
  • The size of the femur and tibia bones.The number of fingers and toes is taken into account.
  • Abdominal circumference.
  • Frontal-occipital size and bipariental parameters of the head of the embryo.
  • Head circumference.
  • The length of the nasal bone. The norms of the object under consideration are: 3.7-7.3 mm at 16-17 weeks of gestation, 5.3-8.1 mm at 18-19 weeks, 5.8-8.3 mm at 20-21 weeks. If the previous indicators are normal, but there are deviations from this component, it is considered that the fetus has no chromosomal abnormalities.

  • The age of the fetus is initially determined incorrectly.
  • The embryo develops with certain pathologies.

3. Anatomical information

The doctor fixes the following nuances:

  1. The presence of the kidneys, their symmetry.
  2. The location of the internal organs: bladder, lungs, stomach, etc.
  3. The structure of the facial bones. This ultrasound can reveal defects in the anatomy of the upper lip.
  4. The structure of the heart in the four-cut.
  5. Sizes of cerebellum, lateral ventricles of the brain, large cistern of the embryo.

5. Amount of amniotic fluid (amniotic fluid)

With insignificant shallow water, therapeutic measures are limited to vitamin therapy, dietary correction, limitation of physical exertion.

Severe water scarcity requires more serious measures that will include taking special medications. This is due to the fact that such a phenomenon can adversely affect the development of the limbs and spinal column of the embryo, provoke abnormalities in the nervous system. Often, children who have matured in low-water conditions suffer from mental retardation and thinness.

No less dangerous for the fetus is pronounced water discharge. A pregnant woman in such situations is most often hospitalized and complex treatment prescribed.

6. The number of umbilical cord vessels

The normal condition is when the fetus has two arteries and one vein.

In those situations when the ultrasound scanner revealed fewer vessels, you should not panic. Good results of the biochemical analysis of blood, as well as the absence of abnormalities in the development of the fetus (according to ultrasound diagnostics) indicate that the single artery completely compensated for the absent work.

In the future, parents should monitor proper nutrition, strengthen the protective reactions of the body of the baby.

Triple test

After passing the ultrasound examination, the pregnant woman will have the next stage of screening: biochemical analysis of venous blood.

The main task of this test is definition of three indicators:

1. Free estriol - sex hormone, which makes itself felt from the first days of the formation of the placenta, and the level of which increases with each month: 1.18-5, 52 ng / ml at 16-17 weeks of pregnancy, 2.42-11.20 ng / ml in the 18-19 weeks, 3,9-10,0 in 20-21 weeks.

  • There is a threat of miscarriage.
  • There are certain anomalies in the development of the neural tube of the embryo or its internal organs. In particular, this concerns the adrenal glands.
  • In the structure of the placenta there were serious violations.
  • There is an intrauterine infection.
  • The fetus is diagnosed with Down syndrome.
  • At the time of delivery of the triple test, pregnant women were treated with antibiotics.

  1. Pregnancy is multiple.
  2. The weight of the embryo exceeds the allowable rate.

2. Free beta hCG. It is this indicator that favors the appearance of the second strip when passing the pregnancy test.

The level of human chorionic gonadotropin in the second trimester of pregnancy can vary: 10-57 thousand ng / ml on the 16th week, 8-57 thousand ng / ml on 17-18 weeks, 7-48 thousand ng / ml on 19- th week of pregnancy.

  • The embryo develops with Down syndrome (2 times abnormal).
  • A woman carries more than one child.
  • There are pathologies associated with increased blood pressure, swelling. Urinalysis in this case states the presence of protein.
  • A pregnant woman is diagnosed with diabetes.
  • The fruit develops with certain defects.
  • There are pathologies in the structure of the ovum. In 40% of cases, this phenomenon can trigger the appearance of choriocarcinoma.

  1. There is a threat of miscarriage.
  2. The embryo does not develop correctly or does not develop at all.
  3. The death of the embryo occurred.
  4. The placenta is not able to fully perform its functions due to violations in its structure.
  5. The fetus has Edwards syndrome or Patau syndrome.

3. Alpha-fetoprotein (AFP). This protein is produced in the liver or in the gastrointestinal tract of the embryo, starting from the 5th week of pregnancy.

Amniotic fluid promotes the release of AFP into the mother’s circulatory system, and from the 10th week of pregnancy the level of this protein gradually increases.

At 15-19 weeks of gestation, the allowable rate of alpha-fetoprotein varies between 15-95 U / ml, after the 20th week - 28-125 U / ml.

  • The doctor incorrectly determined the duration of pregnancy (if deviations from the norm are not so significant).
  • The fetus has Edwards syndrome / Down syndrome.
  • The death of the embryo occurred.
  • There is a risk of abortion.
  • Fetal egg has certain anomalies (bubble skid).

  • There are errors in the structure of the fetal neural tube.
  • The intestine or duodenum of the embryo have malformations.
  • The baby has Meckel's syndrome (in extremely rare cases).
  • Necrosis of the liver, which was the result of infection of the pregnant woman.
  • There are anomalies in the structure of the anterior abdominal wall.

If ultrasound confirms multiple pregnancy, doctors rarely prescribe a biochemical screening: the existing norm values ​​are applicable to singleton pregnancies.

It is very difficult to determine exactly how the indicators will change if a woman bears two or more fetuses.

Bad second screening - what to do and where to go next?

The doctor can calculate the risk of the presence of certain pathologies in the fetus by carefully examining the results. all tests second screening.

However, if the screening program concludes with a risk of 1: 250, a pregnant woman should turn to genetics. This specialist may prescribe additional non-invasive diagnostic methods, by means of which the presence / absence of chromosomal or congenital abnormalities in the fetus is determined.

Prenatal first trimester test

The optimal duration of the first prenatal screening is 10-13 weeks of pregnancy. The purpose of this safe comprehensive examination (ultrasound + double test) is to identify at the early stage possible anomalies and indirect symptoms of the presence of defects in the fetus.

The interpretation of the results of the screening is performed using special tables that contain the norms established by the specialists, taking into account the duration of the pregnancy.

Prenatal test of the first trimester begins with an ultrasound of the fetus. Based on the data obtained and taking into account the norms given in the table, the doctor can confirm or deny the presence of pathologies.

Decoding ultrasound KTR and indicators of TVP

The first thing that the doctor draws attention to during the ultrasound of an embryo is its CTE (coccyx parietal size). The first trimester KTP norms are compared with the values ​​given in the table below:

Indicators KTR in combination with the weight of the fetus is often used to determine the duration of pregnancy.

Minor deviations from the norm suggest that a child can be born either large or small.

If prenatal screening revealed that KTP values ​​are too high, then additional studies confirm the presence of anatomical defects in the fetus.

KTR significantly below normal can be in two cases:

  1. improperly established period of pregnancy (do re-ultrasound after 7 - 10 days),
  2. the embryo stopped in development, which threatens him with death.

It is possible to eliminate the death of the embryo when a heartbeat of normal frequency is detected. Otherwise, curettage of the uterus is performed.

In the process of ultrasound, much attention is paid to the study of TVP (collar space thickness), the indicators are not deviated from the norm, if they have the following values:

These norms may be slightly lower, but their increase will clearly indicate the development of pathology in the unborn child.

The higher the number, the greater the likelihood of the development of fetal Down syndrome or another chromosomal abnormality, and there may also be abnormalities in the functioning of the heart.

But to confirm the presence of any chromosomal disease in the fetus only according to the testimony of the ultrasound of the thickness of the collar space, without additional research, in medicine is not accepted.

Therefore, the doctor may prescribe an additional examination in the form of Doppler, as well as the delivery of blood from a vein for biochemical analysis.

BPR and blood biochemistry

Prenatal screening of the first trimester of pregnancy includes the determination of the fetal head BPR, at which the gap between the inner and outer contours of one and the second parietal bones is measured.

In this case, a line combining the outer contours of both parietal bones should run over the visual cusp of the brain.

An incorrect measurement distorts the results of prenatal screening of the first trimester, which does not allow to accurately determine the duration of pregnancy.

At the same time, for the first trimester weeks, the specialists established a specific normative value of the BPR of the embryo, which can be seen from the following table:

If the prenatal screening test of the first trimester shows that the BPR of the head of the embryo is significantly deviated from the permissible values, the doctor prescribes additional studies.

Increased BPD may be a symptom of the presence of a brain tumor or hernia, the development of hydrocephalus.

In the first case, pregnancy is interrupted, with hydrocephalus prescribed treatment with antibiotics.

A strongly underestimated BPR of the head of the embryo does not bode well either, since it is a symptom of underdevelopment of the brain. As a rule, such pregnancy is interrupted.

Screening for the first trimester includes another important indicator - the size of the nasal bone. This marker, like TVP, can be a sign of the development of Down syndrome in the embryo.

Despite the fact that prenatal examination at an early period (10-11 weeks) does not allow us to estimate the size of the nasal bone, during this period it is still visualized on the screen.

Already at 12-13 weeks, prenatal ultrasound should show that the nasal bone is normal, the size is considered to be at least 3 mm.

Prenatal first biochemical screening includes an examination of the level of two hormones, because of what it is also called "double test".

Biochemical screening helps to identify and determine the level of hCG in the blood of the expectant mother, as well as to examine the blood plasma for the presence and amount of protein (PAPP).

Both substances mentioned are in the blood only in women carrying a child.

As soon as the prenatal first biochemical screening was carried out, the interpretation of the finished results is carried out taking into account the established standards:

  1. The first trimester hCG level should be 0.5 - 2 MoM,
  2. PAP level of the first trimester should be from 9 to 13 weeks - 0.17 - 6.01 MDU / ml.

A strong deviation from the established standards of the prenatal test can be a symptom of the development of Down and Edwards syndromes, but only a doctor can judge about the presence of such pathologies, but taking into account additional examinations.

Prenatal biochemical test of the second trimester

If the prenatal test of the 1st trimester allows to detect up to 95% of cases of chromosomal abnormalities, then the timely conducted prenatal screening test of the second trimester is no less informative in this regard.

But the main purpose of the second prenatal examination is to detect defects in the neural tube and other fetal malformations, as well as to carry out calculations that subsequently reveal the risk of congenital hereditary or chromosomal diseases, among them:

  1. patau syndrome,
  2. hereditary diseases Shershevsky-Turner syndrome and Smith-Opitz syndrome,
  3. polyploidy.

As a rule, after the mother passes the first comprehensive examination, screening for the second trimester is prescribed either at the request of the prospective parents or at the doctor's prescription in specific cases.

Screened for 2 trimesters for a period of 16 to 20 weeks. Evaluation of biochemical parameters of the blood of the expectant mother is carried out in 16 - 18 obstetric weeks.

Before giving blood for analysis, a pregnant woman should have first-trimester ultrasound signs with her, indicating the exact duration of pregnancy.

Before donating blood for a biochemical analysis, the doctor referring the pregnant woman for examination, fills out with her 2 screening questionnaire, which indicates the results of ultrasound, the timing, the parameters of TVP and CTD.

All this is the data of ultrasound examination of the first trimester, since it is too early to do the second ultrasound at 16-18 weeks, it is carried out at 20-21 weeks.

The pregnant woman takes the questionnaire filled out according to all the rules to the laboratory, where blood is taken for HCG, AFP and NEZ.

The main thing is to pass tests on an empty stomach, and on the eve of the procedure, do not eat too salty, spicy and fatty foods, which can distort the results.

When the results of the biochemical screening of the second trimester are ready, the doctor examines the information obtained and, comparing with the established standards of the triple test, gives the expectant mother recommendations or prescribes additional procedures.

When is ultrasound diagnosed?

Screening ultrasound is usually performed 3 times, as it is customary to divide the period of gestation into 3 trimesters.

The first screening is done from the 10th to the 14th week of pregnancy., and often only this study implies a double test: in addition to ultrasound, the analysis of the venous blood of a pregnant woman is performed. The results of such a procedure with exact statistical probability determine how the development of dangerous anomalies in the fetus is possible.

Second ultrasound screening usually does not include other tests.. An exception is the suspicion of pathology in the first study or of women of the so-called risk groups. Ultrasound examination for 2 trimesters is done from the 18th to the 20th to the 24th week from the day of the last menstruation. Compliance with the exact dates is very important, since if they do not correspond, the decoding of the ultrasound is considered to be inaccurate.

Who needs the second screening and why?

2 screening ultrasound in our country is prescribed to each pregnant woman, regardless of the presence of complaints. But you should be especially careful when examining pregnant women from risk groups. These include:

  • first-pregnant over 35 years old
  • persons of close marriage,
  • pregnant women with a burdened obstetric and gynecological history,
  • parents suffering from alcoholism and drug addiction.

But all other expectant mothers should treat the second ultrasound screening responsibly so as not to miss the occurrence of pregnancy-threatening pathology at an early stage. Compliance with the results of screening and ultrasound standards will allow a woman to feel calm, knowing that she and the child are all right.

What indicators are evaluated by screening for the 2nd trimester?

During the second trimester ultrasound, the sonologist will necessarily pay attention to the compliance of the fetal size (fetometric indicators) with the period of gestation. There are also a number of special signs, markers, which are usually judged on the presence of anomalies and defects in a child.

The specialist, among other things, evaluates:

  • violation of the formation of the bones of the skull (nasal bone, bones of the hard palate),
  • the size and structure of the lungs, their maturity,
  • the state of the internal organs (for example, the formation of cavities of the heart and blood flow in them),
  • the presence of all the fingers and toes (changing their number indicates internal disturbances).

Values ​​in the normal range for fetal ultrasound do not allow the doctor to complete the study. Additionally, it is necessary to assess the state of the reproductive system of the mother, as this is very strongly reflected in the course of pregnancy. Степень зрелости плаценты, состояние матки и яичников и количество околоплодных вод — важные значения, оцениваемые в каждом из 3 триместров беременности.

Расшифровка заключения УЗИ

После исследования специалист обязательно выдает женщине заключение. But for an unknowing person such data is hardly informative. Traditionally, the sonologist does not diagnose, but sends the pregnant woman to the local gynecologist, who advises the patient on all issues of interest.

If the expectant mother has to wait for consultation of the attending physician for several days, she will certainly take an interest in complying with the results of perinatal screening in advance. It should be remembered that a doctor always judges a pathology only on the basis of a set of indicators of fetometry, and almost never it is disturbed by any one value.

Each child is unique even before birth. And if the expectant mother has really serious reasons for concern, the ultrasound specialist will inform her immediately. Nevertheless we will tell about the main indicators of the second screening and their values ​​are normal.

Body length and fetal weight

At the beginning of the second trimester, the embryo is growing very actively and it is difficult to judge the standards. On average, the length of the fetus increases from 10 to 16 cm between the sixteenth and twentieth weeks of pregnancy. Here it is important to take into account not an absolute indicator in centimeters, but an increase in growth by weeks.

If something is alarming the specialist, a pregnant woman will be offered a second study after a week or two.

Fetometric indicators of the fetus

Fetal weight can only be determined by ultrasound using special formulas. Therefore, this value can be very inaccurate depending on the device, doctor and child’s posture in the womb. With a weight of about 300 grams by the 20th week, all the organs of the child are fully formed, and from 22 weeks or about 450 grams, a baby born prematurely can survive. It seems incredible!

Abdominal circumference and head

As well as the height of the child, these important values ​​vary widely and should strictly correspond to the gestational age. There are often cases when the "developmental lag" in practice turned out to be an incorrectly diagnosed period of pregnancy. However, the widespread introduction of ultrasound diagnostics of early terms reduced the number of such errors.

The results of measuring the circumference of the head and abdomen of the fetus and their compliance with the age norm are shown in the table.

Norms of abdominal circumference and fetal head circumference in millimeters

Biparietal (BPR) and frontal-occipital (LZR) fetal head size

It is not surprising that the entire ultrasound diagnosis of pathologies during pregnancy is based on measurements of the head in 3 projections. It is unlikely that at least one human organ is comparable in complexity and importance to the brain. Normal values ​​of ultrasound for these indicators are also presented in the table.

Table of norms of LZR and BPR

Deviations from the reference values ​​may indicate the formation of serious fetal deformities, such as anencephaly or cerebral edema. But as a rule, such diseases are judged by several repeated ultrasounds.

Bone length: tibia, femur, shoulder and forearm

Some deviation from the norms specified in the table by week of pregnancy is permissible, and can be determined by individual features. The doctor will be alerted by a sharp shortening of the entire limb or a different length of arms or legs in one child.

Another numerical indicator, which necessarily bring in the conclusion of ultrasound due to its importance: amniotic index (AI). This index is obtained by measuring the distance from the body of the fetus to the uterine wall at three points, so that the probability of error is low. Despite the fact that the possible fluctuations of this index are very wide, ranging from 70 to 300 mm, its excess or low values ​​may threaten the development of pregnancy and require urgent intervention by doctors.

Amniotic Index Table


In our time, ultrasound during pregnancy is an indispensable method for the detection of pathologies in apparently healthy patients. It is distinguished by absolute painlessness, safety for the mother and fetus, wide availability. Thanks to the introduction of the three mandatory perinatal screenings, it was possible to help many women and save quite a few children. The article describes in detail at what time and for what purpose the screening of the second trimester of pregnancy is performed.

What it is

Biochemical blood screening is a fairly narrow profile analysis. It belongs to the initial and additional categories of tests. Identifies signs of diseases such as hepatitis B and rubella. In the extended version, the analysis allows to determine the presence of syphilis and HIV in the blood.

Nevertheless, the main function of screening is to identify the susceptibility of the fetus to pathology. Also, the results of the analysis clearly demonstrate how certain diseases develop in the embryo in the future. In this regard, the attending physician is building a phased program of 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. For the appointment of serious hormonal drugs, it is important to know the Rh factor of the pregnant woman and her offspring.

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

Who is shown the procedure

Biochemical screening must be done by every pregnant woman. Some experts question the urgent need for analysis. However, it is unlikely that anyone will guarantee that none of the expectant mothers has serious genetic disorders. The fact is that many women do not even suspect a pathological failure in their bodies, as well as infections. Some moms have a genetic 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 analysis as additional insurance to obtain information about the state of the mother and her child.

Probable risks

Any procedure of intervention in the current work of the body carries certain dangers. In reality, the risks of medical tests are minimized. The first screening slightly increases the chance of fetus loss. This is the biggest risk associated with this type of analysis. Standard screening does not harm the fetus. However, its perinatal varieties, such as chorionic biopsy and amniocentesis, can significantly aggravate the course of pregnancy. In the first case, tissue is taken from the placenta. It will be checked for chromosomes. The risk of losing a fetus in this procedure is about 0.9%. As for the amniocentesis, during it a thin needle is inserted into the stomach to obtain amniotic fluid. This procedure can harm the embryo only because of a medical error. The risk ranges from 0.5%.

It would not be superfluous to single out the categories of women who need primary and repeated screening. These groups may have a high level of risk of having a child with gene pathology. These categories of factors include:

- age above 30 years, if the first pregnancy,
- the presence of serious genetic abnormalities,
- with two or more abortions,
- chronic infectious diseases,
- hereditary pathologies from parents,
- marriage with blood relatives,
- any radiation 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 the first and second trimester. Such factors must be taken into account in the final risk assessment. The most common cause of error analysis is overweight mother. If she is obese, her blood counts will definitely be elevated. If a woman has a significant shortage in weight, then the results will be underestimated.Also a factor in screening rejection is multiple pregnancy. Any risk to calculate here is even theoretically impossible. The rates will be elevated, but this is not always considered a genetic disorder. The fact is that in this case, the test results are divided into two or more embryos. Therefore, even repeated indicators will not lead to a clear picture of what is happening.

Habits can affect the analysis. This is especially true for smoking. Failure can also be fixed if the pregnant woman has a cold during the screening. It is worth noting that this type of analysis is prohibited in diabetes mellitus, as it always gives false results.

Screening preparation

The diagnosis of the body during pregnancy should always be approached seriously and thoroughly. However, preparation in testing is considered to be an equally important step, especially if this is the first blood screening. This analysis reveals specific markers indicating the presence of chromosomal diseases. That is why it is important to do everything to eliminate even the slightest probability of a false rejection.

First, one day before testing it is forbidden to eat foods such as smoked meats, citrus, chocolate, fried, fatty and spicy dishes. Otherwise, instead of serum, fatty elements are formed in the body. During the centrifugation procedure, it will be practically impossible to separate important cells. In any case, this will significantly complicate the test, it will be necessary to re-pass, which may adversely affect the fetus.Analysis should always be done on an empty stomach. It is allowed 4-5 hours before the test to drink some non-carbonated water.

Screening during the 1st trimester

The most appropriate period for conducting a primary biochemical test is 10–13 weeks. In earlier periods, screening is not recommended. The price of such an analysis varies from 1,800 to 2,000 rubles. Based on the results of the initial test, specialists evaluate the health and development of the fetus, as well as the state of the mother.

Screening during the first trimester allows you to identify pathologies such as Down and Edwards syndromes, neural tube defects, heart disease, etc. Before evaluating results, the doctor should always rely on personal examination data such as blood pressure, temperature, mother's weight, and other supporting factors. In parallel with the screening, urine and blood tests are taken for infections. Confirmation of risk is done on the basis of ultrasound.

Screening during the 2 trimester

Biochemical testing is carried out from 15 to 20 weeks of the term. At the end of the trimester, doctors do not recommend screening. The price of this procedure is about 3000 rubles. It includes several tests at once. First, chromosomal abnormalities are detected. Secondly, damage to the body of the embryo is found, in particular in the abdominal cavity and the spine. The analysis also allows predicting the development of fetal Down syndrome. Closer to week 20, the embryo is already quite large. Therefore, it is possible with a minimum risk to take a sample of amniotic fluid. This type of screening is called amniocentesis. It is contraindicated to do with the tone of the uterus.

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

Decoding and norms of indicators (1 trimester)

Perinatal diagnosis in the first weeks of pregnancy consists of identifying several important characteristics of the blood and genes. The most significant of them are chorionic gonadotropin (abbreviated - HCG) and PAPP protein. These are extremely important hormones on which the course of pregnancy directly depends.

From 10 to 12 weeks, rates of 20 to 95 thousand mU / ml are considered the norm for hCG. Allowed deviation of 1-2 thousand units. The rate of hCG at week 13 is 15-60 thousand mU / ml.

The PPAP protein in the last month of the 1st trimester should be in the range of 0.3 to 6 mU / ml. At the 10th and 11th week the normal values ​​are 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 age and weight of the pregnant woman, the MoM coefficient is used. With this medial index, deciphering of the first trimester biochemical screening is facilitated. Here, the acceptable range is 0.5-2.5 units.

Decoding and norms of indicators (2 trimester)

Biochemical screening for 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 present a detailed picture of the development of the fetus.

The rates of biochemical screening for the 2nd trimester for AFP are from 15 to 95 U / ml. By the end of the period, indicators may increase to 125. The level of hCG in the first half of the trimester should be from 8 to 58 thousand mU / ml. By the end of the period, the figures dropped 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 values ​​are 7.5 nmol / l.

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

Reasons for rejection of hCG

The results of biochemical screening do not always give 100% certainty of the presence or absence of a genetic abnormality. Minor deviations from the norm may occur due to a variety of reasons. However, they should not be paid attention to if all other tests are in order.On the other hand, a significant increase in the level of hCG indicates a trophoblastic disease in the mother, as well as a multiple pregnancy. Decreased rates may be due to ectopic fetal development. If the fear was confirmed by ultrasound, the risk of a genetic disease becomes real.

Deviations of other indicators

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

Increased levels of AFP increase the risk of CNS malformation, umbilical hernia, liver necrosis. If the level of this hormone is greatly reduced, there is a possibility of premature fetal death. Also, the AFP may signal Down syndrome.

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