Whether non-invasive DNA is necessary or not needs to be combined with the clinical and Down’s syndrome results. Normal results of Down’s syndrome screening test usually do not require non-invasive DNA. Non-invasive DNA has a high accuracy in screening malformations, NT test is needed at 11-13 weeks +6 of pregnancy, Down’s syndrome screening is needed at 15-20 weeks, and further non-invasive DNA or amniocentesis is needed for further screening in case of abnormality, and regular prenatal checkups and postpartum diagnosis are performed to screen and intervene for congenital defects of the fetus in a timely manner. High risk or critical risk in Down’s syndrome screening requires further non-invasive DNA or even amniocentesis for further screening of fetal malformations. Regular and good pregnancy tests are needed during pregnancy, and the screening program is determined clinically. For the sake of eugenics, you must eat a reasonable diet during pregnancy, eat more fresh fruits and vegetables, drink more pure milk, avoid smoking and alcohol, and stay away from harm. If you have any discomfort or other abnormalities during pregnancy, you need to go to the hospital in time to deal with them.