What is Down syndrome screening?

For people who are not pregnant, Down syndrome screening may be relatively unfamiliar. However, Down syndrome screening is a very familiar test for families with pregnant women. Some people may think that Down syndrome screening is quite dangerous. In fact, Down syndrome screening only involves drawing serum from pregnant women to check whether the fetus is deformed or has Down syndrome. Down syndrome screening is relatively accurate.

Down syndrome screening is the abbreviation for prenatal screening test for Down syndrome.

The purpose is to test the blood of pregnant women to detect the concentrations of alpha-fetoprotein, human chorionic gonadotropin and free estriol in the maternal serum, and to determine the risk factor of the fetus suffering from congenital idiocy and neural tube defects based on the age, weight, gestational age of the pregnant woman.

Currently, the Down syndrome screening test tests the concentration of alpha-fetoprotein and human chorionic gonadotropin in the pregnant woman's blood, and combines it with the pregnant woman's age to use a computer to accurately calculate the risk of the pregnant woman carrying a fetus with Down syndrome.

Alpha-fetoprotein (AFP) generally ranges from 0.7 to 2.5 MOM (multiples of the median).

The higher the level of chorionic gonadotropin, the higher the chance that the fetus will have Down syndrome. In addition, the alpha-fetoprotein value, human chorionic gonadotropin value, and the pregnant woman's age, weight, and weeks of pregnancy can be entered into the computer, which will calculate the risk of the fetus developing Down syndrome. Different hospitals use different standards. If the probability indicated by the test result (such as 1/100) is greater than the normal reference value probability (such as 1/275), the result is positive, indicating that the fetus has a higher chance of being sick and further amniocentesis or chorionic villus sampling should be performed.

AFP (alpha-fetoprotein): AFP is a fetal-specific globulin.

The molecular weight is 64,000 to 70,000 Daltons. It may have the immunomodulatory function of glycoprotein during pregnancy and prevent the fetus from being rejected by the mother. AFP is synthesized by the yolk sac in the first 1 to 2 months of pregnancy, and then mainly by the fetal liver. A small amount of AFP can also be synthesized in the fetal digestive tract and enter the fetal blood circulation.