Noninvasive DNA is an important means of prenatal examination at present. It refers to extracting fetal DNA from pregnant women's peripheral blood, and using the new generation high-throughput sequencing technology combined with biological information analysis, we can accurately get the risk rate of fetal chromosome aneuploidy, that is, 2 1- trisomy syndrome, 18- trisomy syndrome and 13- trisomy syndrome, and judge whether the fetus has congenital genetic diseases. Although the accuracy of noninvasive DNA screening by Bitang is high, it is still a screening test, so the conclusion given is the risk value. According to the standard of risk value, low risk or high risk can be obtained. If the non-invasive results suggest high risk, it means that the probability of fetal congenital hereditary diseases is relatively high, but it can not be used as a basis for diagnosis, and it is impossible to decide whether to keep the fetus according to the non-invasive results. For those who need further amniocentesis for diagnosis without high risk, amniocentesis is a diagnostic method. If amniocentesis determines that there is no problem with the fetus, it can be kept. If amniocentesis determines that the fetus has chromosomal diseases, the pregnancy can only be abandoned.