Second screening in pregnancy

The second screening during pregnancy includes a blood test that determines three types of hormones: free estriol, hCG, AFP (in some cases, inhibin A is determined). Deviations from the normal indicators indicate abnormalities in the normal development of the fetus.

The term screening has only recently come into use among medical professionals.

Screening means special tests that can determine changes in the hormonal background of a pregnant woman. Such tests can identify possible congenital defects in the fetus (for example, Down syndrome).

Screening includes venous blood analysis and ultrasound examination. All the smallest nuances of the pregnancy are taken into account, as well as the physiological characteristics of the pregnant woman - age, weight, height, existing bad habits, intake of hormonal agents, etc.

Throughout the pregnancy, two screenings are performed, which are done at intervals of several weeks (there are also some differences between the first and second screening).

The first screening is carried out at 11-13 weeks of pregnancy, the second at 16-18 weeks.

Timing of the second screening during pregnancy

The second screening during pregnancy is usually prescribed by a gynecologist between the 16th and 20th week of pregnancy.

Some doctors believe that the second examination is best performed between 22 and 24 weeks, but most specialists believe that screening at 16–17 weeks is more informative.

Second biochemical screening during pregnancy

Biochemical screening allows the gynecologist to assess the health of both the mother and her future child. Also, the second screening during pregnancy excludes possible developmental disorders in the child, termination of pregnancy, assesses the condition of the placenta and umbilical cord, and suggests possible defects (for example, heart disease).

The second screening examination includes an ultrasound examination, blood analysis and interpretation of the results. A special role is given to the interpretation of the tests, since not only the life of the baby, but also the psychological state of the woman depends on the correctness of the doctor's assessment of the child's condition in the womb.

A biochemical blood test determines three indicators (estriol, hCG, AFP), the level of which is used to judge the development of genetic disorders in a child.

Second screening during pregnancy by ultrasound

The second screening during pregnancy using ultrasound makes it possible to identify a large number of developmental disorders and anatomical defects in the future child.

Ultrasound at 20-24 weeks shows the main anatomical developmental abnormalities, such as heart defects, brain defects, kidney defects, abnormal development of the gastrointestinal tract, facial anomalies, and limb defects.

Pathologies detected at this stage are not subject to surgical treatment; in this case, termination of pregnancy is recommended.

Ultrasound can also be used to assess possible chromosomal abnormalities (growth delay, polyhydramnios, oligohydramnios, cysts, short tubular bones and some others).

Screening ultrasound at 16-19 weeks is prescribed if necessary, when it is necessary to assess the likelihood of the fetus developing chromosomal abnormalities.

Norm of the second screening during pregnancy

Some specialists do not explain how to decipher the second screening during pregnancy of the expectant mother.

Indications corresponding to normal fetal development should be as follows:

• AFP, weeks 15-19 – 15-95 units/ml, weeks 20-24 – 27-125 units/ml
• HCG, 15-25 weeks – 10,000-35,000 mIU/ml
• Esterol, 17-18 weeks – 6.6-25.0 nmol/l, 19-20 weeks – 7.5-28.0 nmol/l, 21-22 weeks – 12.0-41.0 nmol/l

Second screening indicators during pregnancy

The second screening during pregnancy is performed to detect possible chromosomal abnormalities in the fetus. The second screening usually prescribes a "triple test" - a blood test for hormone levels:

• estriol (produced by the placenta, low levels indicate developmental pathologies in the unborn child)
• AFP or alpha-fetoprotein (a protein that is present in the mother's blood only during pregnancy; if the level is low or high, the condition of the unborn child is disrupted; a sharp increase in protein indicates the death of the fetus)
• HCG or human chorionic gonadotropin (begins to be produced in the first days of pregnancy, a low level indicates pathologies in the development of the placenta, an elevated level indicates chromosomal abnormalities, gestosis and some other pathologies).

If necessary, a test for inhibin A levels is prescribed; a reduced level of inhibin A indicates chromosomal pathologies (Down syndrome, etc.).

The AFP level in Down syndrome decreases, and hCG increases.

In Edwards syndrome, a decreased level of hCG is observed, other indicators are within normal limits.

Elevated AFP levels may indicate fetal kidney abnormalities or abdominal wall abnormalities.

It is worth noting that Edwards and Down syndrome can be detected by screening only in 70%. To avoid mistakes, the doctor must evaluate the blood test results together with the ultrasound results.

If the blood test is normal, the doctor assesses the child's development as normal. With minor deviations in one direction or another, one cannot immediately assume pathologies, since testing often turns out to be false, in addition, there are some factors that can affect the results (for example, multiple pregnancies, diabetes, smoking, inaccurate determination of the term, excessive weight of the pregnant woman).

No doctor can terminate a pregnancy or make a diagnosis based solely on the results of screening. This testing only allows one to assess the probability of congenital pathologies in a child. If a woman has a high probability of giving birth to a child with pathologies, she is prescribed a number of additional studies.

Results of the second screening during pregnancy

The second screening during pregnancy can sometimes show bad results, but this is not a reason to despair and panic ahead of time. The screening results may indicate a high probability that some abnormalities are possible, but do not confirm this 100%.

If the second screening showed a significant deviation from the norm of at least one of the indicators, the pregnant woman is prescribed additional examination.

There are also a number of factors that can affect the results of screening tests:

• in vitro fertilization;
• excess weight during pregnancy;
• presence of chronic diseases (diabetes mellitus);
• bad habits of the expectant mother (smoking, drinking alcohol, etc.).

It is worth noting that if a woman is pregnant with twins (triplets, etc.), then conducting a biochemical blood test is considered inappropriate, since in this case, all the woman's indicators will be higher than normal and it will be almost impossible to calculate the risks of developing developmental disorders.

The second screening during pregnancy allows the woman and her doctor to obtain information about the condition of the fetus, its development, and how the pregnancy is progressing. Doctors prescribe a screening study in the first two trimesters; in the third trimester, screening is done only if necessary.

Conducting such an examination should not cause any concerns for a pregnant woman; the vast majority of women respond positively to screening.

It is recommended that all screening tests during pregnancy be done in one laboratory, which will make it easier for the doctor to interpret the results.