Terms of the third screening for pregnancy
The specified terms of biochemical and ultrasound screenings were chosen not accidentally, but are dictated by the fact that it is at these terms of bearing the child that the most important changes in his intrauterine development take place. So, the basic formation of the fetal organs systems by the 10-11th week is completed, and the pregnancy from the embryonic period enters the fetal, which lasts until the birth of the child.
Biochemical screening (blood test) of a pregnant woman is performed if she is at risk of having a child with Down syndrome, Edwards syndrome or neural tube defect (spina bifida, anencephaly, hydrocephalus). This group of doctors includes women who first became pregnant at the age of 35 and older, the presence of hereditary diseases among close relatives, previous births of sick children, as well as repeated spontaneous abortion (habitual miscarriages) in women. Biochemical screening is carried out by examining the blood level of human chorionic gonadotropin, alpha-fetoprotein and free estriol. The data of these analyzes with a sufficiently high degree of reliability make it possible to determine the risk of the appearance of the above pathologies in the child.
Ultrasound examination of structural malformations of the fetus is mainly based on the use of ultrasound in the second trimester of pregnancy. For example, the threat of Down syndrome is revealed by the thickness of the collar space in the fetus.
Women who are not at risk are ultrasound screenings that are performed three times during pregnancy. The exact terms of the third screening for pregnancy are related to the fact that during this period - at the 30-32th week - the growth and weight of the fetus increase, the head grows and the brain mass increases, the lungs develop intensively, the skin integrable and the subcutaneous adipose tissue. The volume of amniotic fluid in the uterus increases, and by 31-32 weeks the child should assume the position upside down - a physiologically normal presentation.