Second screening during pregnancy - deciphering indicators and norms. At what weeks is the second screening carried out: timing, norms and interpretation of indicators during pregnancy Number of umbilical cord vessels

If there are certain indications or at the request of a pregnant woman, at approximately 16 weeks of pregnancy, doctors can conduct a second screening - a simple but very informative procedure. We will talk about the prerequisites for conducting the analysis and what parameters are studied with its help in this article.

In 2000, pregnant Russian women began undergoing screening. This concept refers to a set of studies that help identify the risks of developing genetic mutations in an unborn child. It is with the help of this procedure that you can find out whether the baby will have Down syndrome, Edwards syndrome or abnormalities in the development of the neural tube.

There are 2 screenings for pregnant women, both studies consist of ultrasound diagnostics, as well as a detailed biochemical blood test. The first time the procedure is carried out is at 10-12 weeks of gestation, the second screening occurs at 16-20 weeks of pregnancy. In rare cases and only if certain prerequisites are met, a third screening can be performed on a pregnant woman.

Second trimester screening is not a mandatory procedure and can be performed for a fee at the request of the woman or when certain indications are present. Such indications include the following factors:

blood relationship between the baby’s parents;
the presence of genetic diseases along the family line;
woman's age exceeding 35 years;
previous pregnancies with children with developmental anomalies;
miscarriages, frequent threats of miscarriage;
an infectious disease suffered during the current pregnancy;
taking medications that can negatively affect the health of the fetus;
poor results of the first screening, during which a high risk of developing anomalies in the child was identified;
the presence of neoplasms in a woman’s body.

What parameters does the second screening examine?

During the second screening, an ultrasound is often performed. This diagnosis allows you to examine the fetus, placenta and internal organs of the mother. During ultrasound diagnostics, the doctor pays attention to the following parameters:

dimensions of the baby’s spine, head, abdomen and chest;
proportionality of the limbs and other parts of the child’s body;
state of the brain, degree of development of the cerebellum and cerebral ventricles;
size and degree of development of the intestines, bladder, kidneys, liver, stomach;
condition of large vessels and heart;
structure and main facial features.

Ultrasound during the second screening makes it possible to evaluate not only the child, but also the thickness, structure and degree of maturity of the amniotic sac, the amount of amniotic fluid, the location of the child in the womb, the presence or absence of abnormalities in the cervix or uterine appendages.

In addition to the ultrasound examination, during the second screening, blood is taken for biochemical analysis. It allows you to study 4 main indicators:

Alpha-fetoprotein, abbreviated as ACE. This substance is a fetal blood serum protein. ACE is produced by the embryo's body from about 3 weeks after fertilization. Protein is responsible for the delivery of nutrients to the baby’s blood, provides the child with protection from estrogens and an overly strong reaction of the maternal immune system.
Human chorionic gonadotropin is the second indicator that is necessarily examined during the biochemical blood test when the second screening is done. HCG begins to be detected in the blood and urine of a pregnant woman in the first weeks after conception; it is this hormone that almost all pregnancy tests react to. Human chorionic gonadotropin is first produced by the chorion, and then by the amniotic sac. HCG directly indicates the state of pregnancy, participates in the production of necessary hormones, and supports the normal course of the gestation process.
Free estriol is another hormone that must be tested during the second screening. After the appearance of human chorionic gonadotropin in a woman’s blood, the activity of estriol increases noticeably. This hormone is produced mainly by the child’s liver and amnion, and it is responsible for the supply of blood to the uterus and placenta, the development of ducts in the mammary glands, and the functioning of the female reproductive system.
Sometimes during the screening process of the second trimester, an analysis is carried out for the content of inhibin A, a hormone whose level in a woman’s blood increases sharply after fertilization. Inhibin is produced by women's ovaries, amnion and the child's body. As a rule, inhibin is analyzed extremely rarely during screening and only in cases where a clear picture cannot be drawn from the previous three parameters.

Timing and features of the second screening

As mentioned earlier, second trimester screening consists of two main procedures: ultrasound and biochemical analysis of venous blood. Preparing for ultrasound diagnostics is not difficult. Ultrasound is performed transabdominally, that is, a sensor is applied to the outer surface of the abdomen. There is no need to drink a certain amount of liquid before the procedure, since amniotic fluid already allows you to see a clear picture.

If you do not need to carry out any manipulations before starting ultrasound diagnostics, then it is better to prepare in advance for a biochemical blood test. Preparation, first of all, includes following a certain diet. Approximately 24 hours before screening, you should exclude coffee, chocolate, cocoa, fatty foods, fried foods, exotic seafood and citrus fruits from your menu. At least 6 hours before the test, you need to abstain from food altogether, since blood for such a case is taken on an empty stomach. No later than 4 hours before the start of the procedure, you can drink some plain water.

The timing of the second screening during pregnancy ranges between 16 and 20 weeks. First, an ultrasound examination is performed, and only then, taking into account its results, a blood test for hormones is performed. It is best to perform a second screening between 16 and 17 weeks.

Biochemical analysis indicators are processed by a special program and issued 2 weeks after blood collection.

Second screening: normal indicators

When determining screening standards, the so-called MoM indicator is used. This parameter characterizes the degree of deviation of a particular patient’s indicator from the average value. Normally, MoM should fluctuate between 0.5-2.5 units. If the parameter is close to 1, this means that the hormone indicator is closest to the average in the population. When MoM is above 1, it means the indicator is above the average; when it is less than 1, it means it is below the average value in the population. When calculating the risks of developing certain pathologies, the MoM is adjusted depending on certain factors: the race of the mother, her weight, the presence of bad habits, etc.

If we determine the norms for the values of biochemical parameters, then screening in the second trimester should give the following results:

At the 16th week of pregnancy, the level of hCG in the blood should be from 10 to 58 thousand mU/ml. The level of alpha-fetoprotein at the same period should range from 15 to 95 U/ml. Estriol levels should be 5.4-21 nmol/l.
At weeks 17 and 18, human chorionic gonadotropin levels will vary between 8057 thousand honey units/ml. ACE at the same period will be 15-95 U/ml, and estriol – 6.6-25 nmol/l.
At week 19, the hCG level should normally fluctuate between 7-49 thousand honey units/ml, ACE will be the same as in previous cases, and estriol should be 7.5-28 nmol/l.
By the 20th week of pregnancy, human chorionic gonadotropin will normally vary from 1.6 to 49 thousand honey units/ml. The ACE level will be 27-125 U/ml, and the estriol level, as at week 19, will be 7.5-28 nmol/l.

Now I would like to consider in more detail what anomalies may be indicated by deviations in screening indicators from the norm:

In the case when the level of human chorionic gonadotropin in the blood exceeds the norm or is more than 2 MoM units, the child may be born with Down syndrome or Klinefelter syndrome. If hCG is lower than normal, the likelihood of the baby developing Edwards syndrome increases.
Elevated levels of alpha-fetoprotein in the mother's blood may indicate abnormalities of the fetal nervous system, such as the presence of anencephaly or spina bifida. Often, elevated ACE levels are observed in women carrying more than 1 child. A decrease in this indicator also does not mean anything good and may be evidence of the presence of Down syndrome or Edwards syndrome in the fetus.
Free estriol in the blood may deviate from the norm due to the use of certain medications. These medications include some antibiotics, Prednisolone, Dexamethasone and other drugs. A pregnant woman who is being treated with any medications must indicate this information in her questionnaire filled out before the second screening. In the case when, even without taking medications, the level of free estriol does not reach the normal level, the baby in the womb with a certain degree of probability may have Down syndrome or Edwards syndrome. A reduced estriol level also sometimes indicates fetoplacental insufficiency, abnormal development of the adrenal glands in the fetus, anencephaly, and the threat of miscarriage. An increase in the level of this hormone is often observed when carrying twins, in the case of a large child, as well as in liver diseases.
Inhibin A is elevated if the child has Down syndrome or some other chromosomal mutation. This indicator can only be taken into account in conjunction with other parameters, since there are frequent cases of increased inhibin A levels against the background of normal levels of other hormones. In such situations, children were most often born completely healthy.

Second screening during pregnancy. Video

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

In general, screening in the second trimester of pregnancy is a voluntary procedure. In some cases, the results may be false positive, which causes stress and negatively affects the health of the mother.

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

Ultrasonography

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

Due to the baby’s age, the following indicators can be recorded using an ultrasound sensor:

1. Gender

Sex can be determined if the embryo is positioned appropriately.

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

2. Fetometric data of the fetus

Includes several components:

Length of humerus and forearm bones . The doctor checks the presence of all bone tissues and the symmetry of the forearms.
Dimensions of the femur and tibia bones. The number of fingers and toes is taken into account
Abdominal circumference.
Fronto-occipital size and bipariental parameters of the embryo's head.
Head circumference .
Length of the nasal bone. The norms for the subject of study are: 3.7-7.3 mm at 16-17 weeks of pregnancy; 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 does not have any chromosomal abnormalities.

If there are significant deviations from the norm in all of these indicators, there are two options:

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

3. Anatomical information

The doctor records the following nuances:

The presence of kidneys, their symmetry.
Location of internal organs: bladder, lungs, stomach, etc.
The structure of the facial bones. This ultrasound can reveal defects in the anatomy of the upper lip.
The structure of the heart in a four-chamber section.
Dimensions of the cerebellum, lateral ventricles of the brain, cistern magna of the embryo.

4. Information about the placenta

The most successful place for attachment of the placenta is the posterior wall of the uterus, or the area close to its bottom.

In this situation, if the placenta is located on the anterior wall of the uterus, there is a risk that its detachment will occur in the future.

The structure of the placenta from 16 to 20 weeks should be homogeneous. If there are deviations, treatment is prescribed aimed at normalizing blood circulation.

5. Amount of amniotic fluid (amniotic fluid)

For minor oligohydramnios, treatment measures are limited to vitamin therapy, dietary adjustments, and limitation of physical activity.

Severe oligohydramnios requires more serious measures, which will include taking special medications. This is due to the fact that such a phenomenon can negatively affect the development of the limbs and spine of the embryo and provoke abnormalities in the nervous system. Often, babies who were born in conditions of low water supply suffer from mental retardation and thinness.

No less dangerous for the fetus is severe polyhydramnios. In such situations, a pregnant woman is most often hospitalized and complex treatment is prescribed.

6. Number of umbilical cord vessels

The norm is considered to be a condition when the fetus has two arteries and one vein.

In situations where the ultrasound specialist has identified fewer vessels, there is no need to panic. Good results of a biochemical blood test, as well as the absence of abnormalities in fetal development (according to ultrasound diagnostics) indicate that the only artery fully compensated for the work of the missing one.

If a child is diagnosed with only one vessel on the umbilical cord, he will most likely be born with a low weight, and as he grows, errors in the functioning of the heart may occur. This situation requires regular monitoring by the appropriate doctor.

In the future, parents should monitor proper nutrition and strengthen the baby’s body’s defenses.

7. Parameters of the cervix and uterine walls

The doctor pays attention to the size of the cervix.

If, in comparison with the previous screening, its shortening (less than 30 mm), opening or softening of its tissues is observed, a pessary may be prescribed to maintain pregnancy.

Triple test

After undergoing an ultrasound examination, the pregnant woman awaits the next stage of screening: a biochemical analysis of venous blood.

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

1.Free estriol – sex hormone, which makes itself felt from the first days of placenta formation, and the level of which increases every month: 1.18-5.52 ng/ml at 16-17 weeks of pregnancy; 2.42-11.20 ng/ml at 18-19 weeks; 3.9-10.0 at 20-21 weeks.

A critical (40% or more) decrease in the hormone in question can be a consequence of several phenomena:

There is a risk of miscarriage.
There are certain anomalies in the development of the neural tube of the embryo or its internal organs. In particular, this applies to the adrenal glands.
Serious disturbances have occurred in the structure of the placenta.
There is an intrauterine infection.
The fetus is diagnosed with Down syndrome.
At the time of taking the triple test, the pregnant woman was being treated with antibiotics.

The level of free estriol in the blood of the expectant mother can increase in several situations:

Pregnancy is multiple.
The weight of the embryo exceeds the permissible norm.

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

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

The amount of free beta-hCG in the blood may increase if:

The embryo develops with Down syndrome (with a deviation from the norm of 2 times).
A woman carries more than one child.
There are pathologies associated with increased blood pressure and swelling. In this case, a general urine test reveals the presence of protein.
A pregnant woman is diagnosed with diabetes.
The fetus develops with certain defects.
There are pathologies in the structure of the fetal egg. In 40% of cases, this phenomenon can provoke the appearance of choriocarcinoma.

Low hCG levels may indicate the following:

There is a risk of miscarriage.
The embryo does not develop correctly or does not develop at all.
The embryo died.
The placenta is not able to fully perform its functions due to disturbances in its structure.
The fetus has Edwards syndrome or Patau syndrome.

If the period is incorrectly determined, the hCG level will also not meet the standards.

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 pregnancy, the permissible level of alpha-fetoprotein varies from 15-95 U/ml, after the 20th week - 28-125 U/ml.

The doctor incorrectly determined the gestational age (if the deviations from the norm are not so significant).

The fetus has Edwards syndrome/Down syndrome.

The embryo died.

There is a risk of miscarriage.

The fertilized egg has certain abnormalities (hydatidiform mole).

An increase in the amount of AFP in the blood of a pregnant woman can cause the following phenomena:

There are errors in the structure of the fetal neural tube.
The intestine or duodenum of the embryo has developmental defects.
The baby has Meckel's syndrome (in extremely rare cases).
Liver necrosis, which was a consequence of infection of the pregnant woman’s body.
There are anomalies in the structure of the anterior abdominal wall.

If ultrasound confirms multiple pregnancy, doctors rarely prescribe biochemical screening: existing normal indicators apply to singleton pregnancies.

Determining exactly how the indicators will change if a woman is carrying two or more fetuses is very problematic.

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

If the results are positive, expectant mothers should not immediately panic - in 10% of cases such results turn out to be false.

However, if, according to the conclusion of the screening program, the risk level is 1:250, the pregnant woman should contact a geneticist. This specialist can prescribe additional non-invasive diagnostic methods, through which the presence/absence of chromosomal or congenital abnormalities in the fetus is determined.

If the risk is assessed as 1:100, it is recommended to undergo invasive research methods, or undergo a non-invasive prenatal test:

. It involves testing amniotic fluid, to collect which the doctor pierces the peritoneum. The effectiveness of such an analysis is 99%, but such a procedure can cause a miscarriage in the near future.
Cordocentesis. The material being studied is the umbilical cord blood of the embryo. To collect it, the doctor inserts a needle into the uterus by puncturing the anterior peritoneum. It is advisable to carry out this procedure between 22 and 25 weeks, but not earlier than 18 weeks of pregnancy. The manipulation in question in rare cases can cause intrauterine infection or miscarriage.
Non-invasive prenatal test (NIPT). Can be prescribed as early as the 10th week of pregnancy. To test fetal DNA, the mother's venous blood is used. A sample of embryonic DNA taken through sequencing is checked for a variety of chromosomal abnormalities. A negative result is an almost 100 percent guarantee of the absence of developmental anomalies. If the results are positive, the invasive diagnostic techniques described above are required. .

If invasive diagnostics confirm unfavorable results of the second screening, the woman has two options:

Terminate the pregnancy. The longer the period, the more severe the consequences for the woman’s health and psyche. However, with proper rehabilitation measures, parents will soon be able to start planning their next pregnancy.
Leave the child. When making such a decision, future parents should be familiar with all the difficulties they will encounter when raising a seriously ill child.

Screening is a set of activities that are aimed at identifying possible pathologies in the unborn baby. What examinations should a woman undergo? When is second trimester screening done?

Second screening and examinations that include it

What is included in the 2nd screening during pregnancy? The second perinatal screening is a combination of two examinations: ultrasound and biochemical, although in some cases they are carried out only. Pregnant women undergo a blood test for the following indicators: (human chorionic gonadotropin), AFP (alpha fetoprotein) and free estriol (E3).

During an ultrasound examination, the doctor will find out the following parameters that will help determine the presence or absence of possible pathologies in the baby’s development:

thickness, location, maturity and structure;
condition of the uterus, its cervix and appendages;
volume of amniotic fluid;
(volume of the chest, abdomen and head, length of paired bones on each side);
development of the brain and spine;
facial development (eyes, mouth, nose);
development of the heart and large blood vessels;
condition of vital organs: kidneys, bladder, intestines, stomach.

At what time is the second screening done?

When is the second screening done during pregnancy? This event is carried out in the second trimester of pregnancy. The most suitable time to donate blood for analysis is 16-18 weeks, It is at this time that the screening results will be most reliable. The timing of ultrasound screening for the 2nd trimester is 19-20 weeks.

The second screening is mandatory for all women who are registered at the antenatal clinic, but it is especially indicated for those who have at least one of the following indications:

the parents of the unborn child are close relatives;
the mother suffered an infection during pregnancy;
one of the parents suffers from a genetic disease;
the pregnant woman has already had miscarriages;
the family has children with pathologies of the nervous system and developmental delays;
showed that the fetus has serious developmental disorders.

Some expectant mothers refuse to undergo a second screening because they believe that its results may be false positive or false negative. To do this, it is necessary to write a statement of refusal to conduct this study, which, at the request of the woman, must be provided by the attending physician.

Preparing for the examination

Preparation is necessary just before taking a blood test. To do this, exclude the following foods from the diet per day: fatty and fried foods, chocolates, fruits (citrus fruits only), fish and other seafood, cocoa. Blood is donated on an empty stomach (you cannot eat 5-6 hours before the procedure), but you are allowed to drink a glass of water. Ultrasound examination does not require special preparation.

Interpretation of test and ultrasound results and standards for the second screening

Norms of blood parameters(E3, AFP and hCG) are different for each week of pregnancy:

Week of pregnancy	AFP level (U/ml)	HCG level (mIU/ml)	E3 level (nmol/l)
	15-95	10000-58000	5,5-20
	15-95	8000-57000	6,5-25
	15-95	8000-57000	6,5-25
	15-95	7000-49000	7,6-27
	27-125	1600-49000	7,6-27

The doctor evaluates not only the results of blood tests, but also the data obtained during ultrasound diagnostics. Specialist draws attention to the following points:

the size of the fetus corresponds to generally accepted standards (the child develops according to age);
the face has no pathologies (the eyeballs are developed according to age, the nasal bone is of normal size, there are no clefts on the face);
internal organs (kidneys, liver, heart, lungs, gastrointestinal tract, etc.) are developed according to age, do not have pathologies and possible developmental disorders;
the content of amniotic fluid meets the standards;
has normal thickness, its structure without signs of pathologies.

The norms of several examples of the fetus, which the doctor evaluates using ultrasound screening in the 2nd trimester (16-20 weeks):

A week	Biparietal size (BPD) (mm)	Head circumference (mm)	Abdominal circumference (mm)	Fronto-occipital size (mm)	Femur bone length (mm)	Shoulder bone length(mm)
16	31-37	112-136	88-116	41-49	17-23	15-21
17	34-42	121-149	93-131	46-54	20-28	17-25
18	37-47	131-161	104-144	49-59	23-31	20-28
19	41-43	142-174	114-154	53-63	26-34	23-31
20	43-53	154-186	124-164	56-68	29-37	26-34

Signs of pathologies at the second screening

The results of blood tests are deciphered by the attending physician. Reduced level AFP may indicate Edwards or Down syndrome, fetal death, or incorrect determination of the week of pregnancy. An increased level of AFP indicates malformations of the nervous system, Meckel's syndrome, death of liver cells, esophageal atresia, and umbilical hernia.

Reduced estriol indicates the following fetal defects: intrauterine infection, adrenal hypoplasia, Down syndrome, anencephaly, fetoplacental insufficiency, as well as the risk of premature birth. Elevated estriol indicates liver and kidney diseases in the mother, as well as a multiple pregnancy or a large fetus.

If there is any suspicion of serious pathologies, the doctor will suggest the woman to carry out a procedure called amniocentesis. During it, the peritoneum is pierced and amniotic (amniotic fluid) fluid is taken for analysis. Using this test, you can confirm the presence of pathology with a 99% probability or make sure that there is no danger to the baby. But it should be remembered that this procedure can provoke.

Sometimes the results of the second screening may be incorrect. They are influenced by the following factors:

(with excess body weight, blood counts may be overestimated, if underweight, they may be underestimated) and the age (over 35 years) of the pregnant woman;
taking certain hormonal medications;
abuse of drugs, alcoholic beverages and cigarettes;
chronic diseases of the expectant mother (etc.);
pregnancy resulting from IVF;
multiple births.

Video about the second screening during pregnancy

We offer you to watch a video about the second pregnancy screening.

How many weeks did you have or will you undergo 2nd trimester screening?