The result is “high risk”, which means that the fetus has a higher chance of having the disease, which means that if the blood test is high, the fetus has a higher chance of having the disease. This means that if the blood test is high, there is a higher chance of having a child with Down’s syndrome, but it does not mean that the fetus is necessarily defective. On the other hand, even if the test results are normal, there is no guarantee that the fetus will not have the disease. If the result is “high risk”, amniocentesis or chorionic villus test, or non-invasive DNA test should be performed to rule out the possibility of Down’s syndrome to the maximum extent if the test result is normal. Amniocentesis is suitable for pregnant women from 18 to 22+6 weeks of pregnancy. Non-invasive DNA monitoring is suitable for 1. pregnant women of advanced age (≥35 years old) who do not want to choose invasive prenatal diagnosis; 2. pregnant women with high risk of Down’s syndrome or single index value change who do not want to choose invasive prenatal diagnosis; 3. pregnant women who do not want to choose invasive prenatal diagnosis because of high NT value or other anatomical abnormalities on ultrasound during pregnancy; 4. pregnant women who are not suitable for invasive prenatal diagnosis, such as virus Pregnant women who are not suitable for invasive prenatal diagnosis, such as virus carriers, placenta previa, placenta hypoplasia, low amniotic fluid, RH blood type negative, history of miscarriage, pre-eclampsia or precious children, etc.; 5. Pregnant women who are unwilling to undergo amniocentesis cell culture failure or cannot undergo invasive prenatal diagnosis; pregnant women who wish to exclude fetal trisomy 21, trisomy 18, trisomy 13 and voluntarily choose to perform non-invasive prenatal testing. 6. Pregnant women with positive serum screening and those who have psychological barriers to prenatal diagnosis; Every couple is at risk of having a child with chromosomal disorders. Its occurrence is incidental and random, with no prior warning, no family history and no clear history of toxic exposure, and its incidence increases with maternal age. There is no effective treatment for chromosomal disorders.