Noninvasive critical value represents the results of noninvasive DNA showing a critical value, indicating a high probability that the fetus has a chromosomal abnormality. Non-invasive DNA test results are mainly low risk, high risk and critical risk. Critical values mainly indicate the probability that the fetus has a chromosomal abnormality and there is a possibility that Down syndrome exists, but it is between low risk and high risk. Further amniocentesis is required if the test results are of critical risk or high risk. Pregnant women between 15 and 20 weeks of gestation need to be screened for Down syndrome, and the normal Down’s syndrome screening rate is only about 60% accurate. If the pregnant woman is older than 35 or has other risk factors, then non-invasive DNA testing is an option, and if there is an abnormality then amniotic fluid will need to be drawn from the abdomen at 16-22 weeks of pregnancy for testing. It is recommended to have regular checkups during pregnancy and if any abnormality occurs, it should be dealt with promptly.