Patient's question:
NoDoctor's answer:
Analysis of the condition: Down syndrome screening refers to the screening for Down syndrome (also known as congenital idiocy or macroglossia). It involves taking chorionic villus blood or amniotic fluid for cell culture, followed by karyotype analysis of chromosomes. If the 21-trisomy syndrome karyotype is observed, the fetus can be diagnosed with Down syndrome. During screening, maternal serum is drawn to detect the concentration of alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) in the mother's serum. By combining the mother's estimated due date, age, and gestational age at the time of blood collection, the risk factor for having a "Down syndrome child" is calculated, which can identify 80% of Down syndrome fetuses.Advice: AFP is a specific globulin of the fetus, with a molecular weight of 64,000-70,000 daltons. During pregnancy, it may have immune regulatory functions as a glycoprotein, helping to prevent fetal rejection by the mother. AFP is synthesized by the yolk sac in the early stages of pregnancy (1-2 months), and is then primarily produced by the fetal liver. The fetal digestive tract also produces a small amount of AFP, which enters the fetal bloodstream. AFP levels in fetal blood rise rapidly at 6 weeks of gestation, peak at 13 weeks, and then gradually decline until term. AFP in amniotic fluid primarily comes from fetal urine, and its trends are similar to those of fetal blood AFP. AFP in maternal blood comes from both amniotic fluid and fetal blood, but its trends do not align with those of amniotic fluid or fetal blood. In the early stages of pregnancy, maternal blood AFP levels are lowest and gradually increase as pregnancy progresses, peaking between weeks 28-32, before declining again. Pregnant women carrying a fetus with congenital idiocy have serum AFP levels that are 70% of those of normal pregnant women, with an average MoM value of 0.7-0.8 MoM. It is important not to rely on a single result; Down syndrome screening requires the final result. Please follow up regularly. Wishing you good health.
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