What should you pay attention to before taking Down syndrome screening?

Down syndrome screening is a relatively common examination method. This examination can ensure that both the pregnant woman and the fetus are not in danger. It can also detect whether there are some genes in the pregnant woman's body that may cause Down syndrome in the fetus. However, before doing Down syndrome screening, the patient needs to pay attention to do some related examinations and then cooperate with the Down syndrome screening examination so that the results of the examination are clear, there will be no problems, and it can be dealt with easily.

Down syndrome screening is a safe and convenient test that poses no risk to either the pregnant woman or the fetus. The test is done by testing the concentration of alpha-fetoprotein (AFP) and human chorionic gonadotropin (β-hCG) in the pregnant woman's blood, so the pregnant woman only needs to draw a little blood for the test and there will be no danger.

Unlike general physical examinations involving liver function, Down syndrome screening does not require fasting. Recently, I found that some sisters are not very clear whether they need to fast. This is mainly because Down syndrome screening is abbreviated as "Down syndrome screening", which is very similar to another word "sugar screening" and sounds exactly the same. However, unlike Down syndrome screening, sugar screening is used to screen for gestational diabetes. It is usually done at 24 weeks and requires fasting for 12 hours. Therefore, if you have any doubts or are confused, you might as well ask your doctor which test order is prescribed for you.

How to read Down syndrome screening results

Currently, the Down syndrome screening test tests the concentration of alpha-fetoprotein (AFP) and human chorionic gonadotropin (β-hCG) 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 each pregnant woman carrying a fetus with Down syndrome.

Alpha-fetoprotein (AFP) generally ranges from 0.7-2.5 MOM. The higher the level of chorionic gonadotropin, the higher the chance that the fetus will have Down syndrome. In addition, the doctor will input the alpha-fetoprotein value, human chorionic gonadotropin value, and the pregnant woman's age, weight, and weeks of pregnancy 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.

(1) AFP (alpha-fetoprotein): AFP is a fetal-specific globulin with a molecular weight of 64,000-70,000 Daltons. It may have the immunoregulatory function of glycoprotein during pregnancy and can prevent the fetus from being rejected by the mother.

AFP is synthesized by the yolk sac in the first 1-2 months of pregnancy, and then mainly synthesized by the fetal liver. A small amount of AFP can also be synthesized in the fetal digestive tract and enter the fetal blood circulation. The fetal blood AFP value increases rapidly at 6 weeks of gestation, reaches a peak at 13 weeks of gestation, and then gradually decreases as the pregnancy progresses to full term. The AFP in amniotic fluid mainly comes from fetal urine, and its change trend is similar to that of fetal blood AFP. Maternal blood AFP comes from amniotic fluid and fetal blood, but its change trend is not consistent with that of amniotic fluid and fetal blood. In early pregnancy, the maternal blood AFP concentration is the lowest, gradually increases as the pregnancy progresses, reaches a peak at 28-32 weeks of pregnancy, and then decreases. The serum AFP level of pregnant women carrying congenitally retarded fetuses is 70% of that of normal pregnant women, that is, the average MoM value is 0.7-0.8MoM.