Non-invasive DNA screening and amniocentesis diagnosis have their own advantages and disadvantages, and the diagnostic specifications issued by the Department of Maternity and Childhood of the Health Planning Commission are provided for reference only: 1. risk value <1/350) in pregnant women. (ii) Those with contraindications to interventional prenatal diagnosis (preterm abortion, fever, bleeding tendency, unresolved infection, etc.). (iii) At the time of consultation, the patient is 20+6 weeks of gestation or more and misses the best time for serological screening or misses the time for routine prenatal diagnosis, but requests to reduce the risk of trisomy 21, trisomy 18 and trisomy 13. 2, the cautionary population of non-invasive DNA prenatal screening: (a) high risk of prenatal screening, elderly pregnant women with expected age ≥ 35 years, and pregnant women with other indications for direct prenatal diagnosis. (ii) Pregnant women with <12 weeks of gestation. (iii) Pregnant women with high body weight (weight >100 kg). (iv) Pregnant women conceived by in vitro fertilization-embryo transfer (hereinafter referred to as IVF-ET). (v) Pregnant women with twin pregnancies. (6) Pregnant women with combined malignant tumors. (a) Pregnant women who have a history of delivery of chromosomally abnormal fetuses and one of the spouses has a clear chromosomal abnormality. (2) Pregnant women who have received allogeneic blood transfusion, transplantation, cell therapy or immunotherapy within one year will interfere with the results of high-throughput genetic sequencing prenatal screening and diagnosis. (iii) Fetal imaging tests suspect the possibility of microdeletion microduplication syndrome or other chromosomal abnormalities in the fetus. (iv) High-risk groups of various genetic diseases.