Perinatal screening is carried out to pregnancy time, it is a modern and safe way to make sure of what with the child everything be all right. The research consists of two parts: ultrasonic and biochemical, however there are many reasons for which results can be inexact.
Ultrasonic screening
Ultrasonography is carried out at least three times for pregnancy: in ten-thirteen weeks of pregnancy (first screening), the second time — in sixteen-eighteen weeks, the third — in thirty-thirty three weeks. It helps to reveal possible defects of a fruit, a state and amount of amniotic waters and many other factors. Key parameters by which are guided at diagnosis: KPS (kopchiko-parietal size) and TVS (thickness of vorotnikovy space). For the greatest informational content of KTR has to exceed 45.85 mm, at the smaller sizes of a fruit the data can be not exact. More than 3 mm cause concerns of TVP, it can indicate various violations in development.
Results of ultrasonography can be distorted because of incorrectly put pregnancy term. Usually the doctor is guided by them for specification of term, but sometimes results are adjusted to obstetric data. This analysis also to a great extent depends on quality of the equipment and qualification of the doctor therefore if there are doubts in the diagnosis, it is better to carry out once again screening in other clinic before adoption of important decisions.
Biochemical screening
Biochemical screening represents a research of composition of blood which is conducted on the same day, as ultrasonography, or in 1-3 days. It is necessary to take a blood test on HGCh and PAPPUS-and. HGCh hormone promotes development of cages of covers of a germ, it appears in blood for 6-10 day after fertilization. Increase in beta HGCh in blood can speak about polycarpous pregnancy, pathologies of development of a fruit, diabetes or toxicosis at future mom. The HGCh low level is even more dangerous too - it is sign of extra-uterine pregnancy, threat of a spontaneous abortion, placentary insufficiency and even death of a fruit. The analysis PAPPUS-and is carried out only in the first trimester of pregnancy. Its decrease speaks about presence of chromosomal anomalies at a fruit, about a possibility of syndromes of Down, Edwards, Cornélie de Lange, threat of an abortion. This analysis is very sensitive to pregnancy term therefore the error of statement of term even for a week can lead to the wrong diagnosis. It is necessary to consider that results can be distorted because of some reasons. For example, at the excess weight of mom of the indication often exceed norm, and at excessive leanness, on the contrary, are too underestimated. To calculate risk of pathologies also difficult at polycarpous pregnancy or at in vitro fertilization (ECO). Such offensive oversight as a breakfast before blood donation can even become the reason of the wrong analysis.