Down’s screening is done in the 4th month of pregnancy, between 15-20+6 weeks of pregnancy to be exact. As the screening rate of Down’s syndrome is only about 60%, if the screening result is high or critical risk, pregnant women should not be nervous, but can choose non-invasive prenatal DNA or amniocentesis according to their age and risk level. Down syndrome is a chromosomal disorder characterized by mental retardation, multiple organ and body malformations, and low viability after birth. If the diagnosis of Down syndrome is confirmed by amniocentesis, abortion will need to be induced.