What does the Down syndrome screening test for?
Disease description:
I am six months pregnant and planning to have a Down syndrome screening. I have a question: what exactly does the Down syndrome screening check for?
Doctor's answer (1)
Dr. Zhang Lu
Down syndrome screening mainly involves testing by drawing peripheral blood from the pregnant woman to assess the risk of the fetus having genetic disorders. Specifically, it examines the following aspects:
1. Biochemical markers: These include the concentrations of substances in the pregnant woman's serum, such as alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3). Changes in the levels of these markers are closely related to whether the fetus has Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), or neural tube defects.
2. Maternal information: Combining personal information such as the mother's age, weight, gestational age, etc., the risk coefficient of fetal abnormalities is calculated using specific algorithms.
3. Target conditions for screening: The primary purpose is to screen for serious genetic disorders in the fetus, including Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and neural tube defects (such as anencephaly and spina bifida).
Down syndrome screening is a prenatal screening method, and its results only indicate risk levels, not a definitive diagnosis. If the screening results show high risk or borderline risk, further prenatal diagnostic tests, such as non-invasive DNA testing or amniocentesis, are usually required for confirmation.
