Non-invasive DNA (non-invasive genetic testing for fetal chromosome aneuploidy) is only a means of prenatal screening, and cannot be taken as the final result. Non-invasive DNA suggests that a high risk of trisomy 21 may still be normal at prenatal diagnosis. Non-invasive DNA has an accuracy rate of about 90%, and is a commonly used screening method for chromosomal abnormalities in mid-pregnancy. Non-invasive DNA is used as a means of screening, and if it suggests a high risk, amniocentesis is needed to make a clear diagnosis, and non-invasive DNA has a high risk, while amniocentesis may still be normal. Down’s syndrome, non-invasive DNA, amniocentesis is the clinical screening or diagnosis of fetal chromosomal abnormalities, women should be pregnant after regular obstetric examination, in should be under the guidance of obstetricians to choose their own examination methods.