Non-invasive pregnancy testing is done mainly by taking the fetal free DNA from the peripheral blood of the pregnant woman. The main diseases detected are the common chromosomal aneuploidies, namely Down syndrome, trisomy 21, trisomy 18 and trisomy 13. The diagnostic rate of detection of these three common chromosomal number abnormalities can reach over 99%. The full clinical name of non-invasive is non-invasive prenatal genetic screening, which is mainly suitable for the following aspects: i. Prenatal report with serological screening and imaging showing common chromosome aneuploidy approaching high risk. II. Pregnancy with contraindications to interventional prenatal diagnosis such as preterm miscarriage, fever, bleeding tendency, untreated infection. Third, in a larger gestational week, 20 weeks plus 6 days or more of pregnancy, just within the time available for noninvasive prenatal testing, having missed the best time for serologic screening or missed the time for prenatal diagnosis, but with special requirements for reducing the risk of the three major chromosomal disorders, noninvasive DNA can be performed in this case.