The critical risk of trisomy 21 is not always clear, and further prenatal diagnosis is needed to clarify this. Rigorous prenatal testing is required during pregnancy to screen for fetal risk of chromosomal abnormalities, either through Down’s syndrome screening at 15-20 weeks of gestation or through noninvasive prenatal testing at 12-22+6 weeks of gestation. Neither Down screening nor noninvasive DNA has a 100% detection rate for trisomy 21, so not all of them will be fine if they show a critical risk. If the Down’s test and non-invasive DNA results indicate a critical risk for trisomy 21, prenatal diagnostic methods such as amniocentesis are required to confirm the diagnosis. Prenatal screening during pregnancy that suggests a critical risk for trisomy 21 is not always fine, and further testing is needed to make a definitive diagnosis. Reasonable prenatal checkups during pregnancy not only allow for early detection of pregnancy complications, timely detection of fetal abnormalities, but also allow for assessment of the safety of the pregnant woman and the fetus, and active management to ensure the safety of the mother and baby.