Early screening for Down’s syndrome is usually recommended around 12 weeks of pregnancy, and should be performed no earlier than 11 weeks at the earliest. Down’s syndrome screening is one of the most important screening tests during pregnancy and the main target diseases are trisomy 21, trisomy 18 and open neural tube abnormalities. Early Down screening is a type of Down screening and corresponds to mid-term Down screening. The timing of early Down screening, which is generally recommended around 11-12 weeks of pregnancy, can roughly determine the risk of Down’s syndrome in the fetus. If no abnormality is found in early screening, mid-term screening can usually be done at 16 weeks of pregnancy. If the mid-term screening is also normal, there is no need for further testing and you can wait until 24 weeks of pregnancy to have a 4D ultrasound for a major screening. The accuracy of the test results can be affected by early or late Down’s syndrome screening, so pregnant women should pay attention to the timing of the test. Secondly, the Down’s syndrome screening is done by drawing the peripheral blood of the pregnant woman, and the pregnant woman does not need to fast.