Down’s syndrome screening for pregnant women is mainly done to check if the fetus has congenital developmental abnormalities such as trisomy 21 and neural tube developmental defects. Children with Down syndrome are also known as congenital stupid children. Early pregnancy 11 ~ 14 weeks, you can do the initial Down’s screening through the ultrasound to measure the thickness of the fetal nuchal translucency layer, to check whether the fetal neural development is normal. At 16~20 weeks of mid-pregnancy, the risk of Down’s syndrome is assessed by drawing blood from the vein of the pregnant woman and combining it with her age, gestational week and weight. Down syndrome is a congenital hereditary extra chromosome 21, also known as trisomy 21. It is important to do rigorous screening during pregnancy to avoid congenital developmental abnormalities in the baby.