What does prenatal Down syndrome screening include

I believe many people have seen reports about children with Down syndrome. Down syndrome is a congenital disease with a high incidence rate. Once a fetus suffers from this congenital disease, it will have a serious impact on the fetus's life. Therefore, in order to prevent the fetus from suffering from Down syndrome, doctors will recommend pregnant women to undergo Down syndrome screening. What are the main examination items in the Down syndrome comprehensive screening?

Down syndrome screening is divided into early pregnancy and mid-pregnancy, and what we usually call Down syndrome screening refers to the Down syndrome screening performed in the mid-pregnancy. The types of Down syndrome screening are as follows:

Early Down syndrome screening

Early pregnancy Down syndrome screening combines B-ultrasound examination of fetal nuchal translucency (NT) screening and serum biochemical test results to assess the risk of pregnant mothers carrying a fetus with a chromosomal genetic disease. Early Down syndrome screening can detect a fairly high proportion of Down syndrome and other chromosomal abnormalities. However, since the accuracy of nuchal translucency scanning is determined by many factors, including the level of the ultrasound doctor and the accuracy of the scanner used, early pregnancy Down syndrome screening still has certain shortcomings. If the early Down syndrome screening fails, you can do nothing or do a diagnostic test, such as amniocentesis, to make a more detailed diagnosis.

Mid-term Down syndrome screening

Mid-pregnancy Down syndrome screening involves drawing serum from both mother and baby to test the concentrations of alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) as well as free estriol (uE3) and inhibin A in the maternal serum. The risk factor of giving birth to a child with Down syndrome is calculated based on the increase or decrease of these markers in the pregnant woman's serum and combined with the pregnant woman's expected date of delivery, age, weight and gestational age at the time of blood collection. When a high-risk phenomenon is found in the mid-term Down syndrome screening, a more detailed diagnosis can be made through fetal anomaly screening and amniocentesis or chorionic villus sampling or non-invasive DNA testing.