Down screening, or Down’s syndrome screening, generally refers to maternal peripheral blood serologic screening, in which blood is drawn in mid-pregnancy to check for concentrations of beta-fetoprotein, chorionic gonadotropin, and free estriol in a pregnant woman’s blood. Peripheral blood serologic screening of pregnant mothers is a commonly accepted method of screening during pregnancy. It involves measuring the serum concentrations of beta-chorionic gonadotropin, alpha-fetoprotein, and free estriol in pregnant women, and based on the results of these three values in combination with the age of the pregnant woman, the risk of the fetus for Down syndrome is calculated, and the pregnant woman is differentiated between high-risk and low-risk pregnancies. Pregnant women with high risk results should undergo further amniocentesis to obtain a definitive diagnosis. For pregnant women over 35 years of age or pregnant women with multiple births or twins, non-invasive DNA or amniocentesis is recommended directly for screening or diagnosis. Pregnant women should have regular prenatal checkups during pregnancy and should seek medical attention if they feel unwell.