Second screening for pregnancy

, medical expert
Last reviewed: 19.10.2021

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The second screening for pregnancy includes a blood test that identifies three types of hormones free estriol, hCG, AFP (in some cases, inhibin A is determined). Deviation from the norm indicates a violation of the normal development of the fetus.

The term screening began to be used among physicians not so long ago.

Screening means special tests, with which you can determine the changes in the hormonal background in a pregnant woman. Such tests can identify possible congenital malformations in the fetus (for example, Down syndrome).

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

Throughout the pregnancy, two screenings are done, which are done with an interval 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.

Terms of the second screening for pregnancy

The second screening during pregnancy is usually prescribed by a gynecologist from 16 to 20 weeks of gestation.

Some physicians believe that the second study is better conducted from 22 to 24 weeks, but most experts believe that at 16-17, screening is more informative.

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Second biochemical screening for pregnancy

Biochemical screening allows a gynecologist to assess the health of both the mother and her future child. Also, the second screening during pregnancy to exclude possible violations in the development of the child, abortion, assess the condition of the placenta and the umbilical cord, suggest possible defects (eg, heart disease).

The second screening study includes ultrasound, blood test and interpretation of the results. A special role is given precisely to the interpretation of the analyzes, since the correct evaluation of the doctor's state of the child in the womb depends not only on the life of the baby, but also on the psychological state of the woman.

Biochemical analysis of blood determines three indicators (estirol, hCG, AFP), the level of which is judged about the development of genetic disorders in the child.

Second screening for pregnancy on ultrasound

The second screening for pregnancy with ultrasound makes it possible to determine a large number of developmental disorders and anatomical defects in a future child.

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

The revealed pathologies at this time are not subject to surgical treatment, in this case, abortion is recommended.

Also, ultrasound can be used to evaluate possible chromosomal abnormalities (growth retardation, polyhydramnios, hypochondria, cysts, short tubular bones and some others).

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

Norm of second screening for pregnancy

Some specialists do not explain how to decipher the second screening for the future mother's pregnancy.

Indications corresponding to normal fetal development should be as follows:

  • AFP, 15-19 week - 15-95 units / ml, 20-24 weeks - 27-125 units / ml
  • HCG, 15-25 week - 10000-35000 mU / ml
  • Estirol, 17-18 weeks - 6,6-25,0 nmol / l, 19-20 weeks - 7,5-28,0 nmol / l, 21-22 week - 12,0-41,0 nmol / l

Indicators of second screening for pregnancy

The second screening for pregnancy is conducted to identify possible chromosomal abnormalities in the fetus. The second screening usually assigns a "triple test" - a blood test for the level of hormones:

  • Estirol (produced by the placenta, low level indicates the pathology of the future child)
  • AFP or alpha-fetoprotein (a protein that is present in the mother's blood only during pregnancy, with a decreased or increased level, the condition of the unborn child is disrupted, a sharp increase in protein indicates fetal death)
  • HCG or human chorionic gonadotropin (begins to be produced in the first days of pregnancy, a lower level indicates a pathology in the development of the placenta, elevated - to chromosomal abnormalities, gestosis and some other pathologies).

If necessary, a determination is made of the level of inhibin A, a lower level of which indicates chromosomal pathologies (Down's syndrome, etc.).

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

With Edwards syndrome, there is a lowered level of hCG, the rest are within normal limits.

Elevated AFP indices may indicate abnormalities in the kidneys in the fetus, abdominal wall disorders.

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

If the blood test is normal, then the doctor assesses the development of the child as normal. With minor deviations in one direction or another, one can not immediately assume pathology, since testing is often false, in addition, there are some factors that can affect the results (for example, in multiple pregnancies, diabetes, smoking, inaccurate timing, excessive pregnancy weight ).

Interrupt the pregnancy or make a diagnosis only relying on the results of screening, no doctor can. This testing provides an opportunity to assess the probability of congenital abnormalities in a child. If a woman's probability of having a child with pathologies is high, then she is assigned a number of additional studies.

Results of the second screening for pregnancy

The second screening during pregnancy can sometimes show poor results, but this is not an excuse to despair and panic ahead of time. The results of the screening may indicate a high probability that some anomalies are possible, but do not confirm this by 100%.

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

Also, some factors may affect the results of screening testing:

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

It should be noted that if a woman is pregnant with twins (triplets, etc.), the biochemical blood test is considered inappropriate, since in this case the woman will have all the indicators above the norm and will not be able to calculate the developmental risks of development disorders.

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

Carrying out such a survey should not cause fear in the pregnant woman, the overwhelming majority of women are positive about the screening.

It is recommended to do all screening studies during pregnancy in one laboratory, which will make it easier for the doctor to decipher the results.

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