What are the main items checked in the唐氏筛查 (Down syndrome screening)?
Disease description:
I'm pregnant and have heard that I need to undergo the唐筛 (Down syndrome screening) test. I'd like to know what specific items this screening primarily checks.
Doctor's answer (1)
Dr. Zhang Lu
Down syndrome screening, also known as prenatal screening for Down syndrome, is primarily used to assess the risk of fetal chromosomal abnormalities, such as Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13). The main components of Down syndrome screening include:
1. Ultrasound examination: Usually performed between 11-13 weeks of pregnancy, this primarily observes the fetal nuchal translucency (NT) and nasal bone to evaluate whether the fetus has abnormalities.
2. Serum screening: Divided into first-trimester screening (9-13 weeks of pregnancy) and second-trimester screening (15-20 weeks of pregnancy). This involves drawing the mother's blood to measure markers such as alpha-fetoprotein, unconjugated estriol, and human chorionic gonadotropin (hCG), whose levels are associated with the risk of fetal Down syndrome.
3. Cell-free fetal DNA testing in maternal blood: If the serum biochemical screening indicates a high risk, a cell-free fetal DNA test in maternal peripheral blood may be further conducted between 12-26 weeks of pregnancy to more accurately assess the risk of fetal Down syndrome.
4. Amniocentesis: High-risk pregnant women may require amniocentesis between 14-16 weeks of pregnancy or chorionic villus sampling (CVS) between 7-10 weeks of pregnancy to obtain fetal cells for karyotyping analysis, thereby determining whether the fetus has chromosomal abnormalities.
Down syndrome screening results only provide a risk assessment, not a definitive diagnosis. If the results are abnormal, further invasive testing is required for confirmation.
