NT is the thickness of the nuchal translucency layer detected under ultrasound, and MOM is the value of Down screening. If the NT value is greater than 2.5, it indicates that the fetus is at an increased risk of neural tube abnormality. In this case, non-invasive DNA or amniocentesis can be done at mid-pregnancy, around 20 weeks, to confirm the diagnosis. Ultrasound is needed to detect the thickness of the nuchal translucency layer and blood tests are needed to detect the risk of Down’s syndrome at around 11-13 weeks of pregnancy. Therefore, during the preparation period and after pregnancy, women should also pay attention to avoid bacteria, viruses, drugs and other unfavorable stimuli, and try to adopt eugenics in order to improve the quality of the fetus.