There are two means of fetal DNA testing: one, non-invasive DNA; and two, amniocentesis. Non-invasive DNA is to extract the peripheral blood of pregnant women and then test the chromosomes of the fetus. Because it is in the peripheral blood of pregnant women to test the fetal chromosomes, the detection rate of non-invasive DNA is 95%-99%, which is not a confirmatory test. Amniocentesis directly extracts the fetal amniotic fluid and analyzes the karyotype to determine whether the fetus has abnormal chromosome numbers or chromosome microdeletions or microinsertions. .