Down syndrome trisomy 21 1:380 suggests a critical risk, which is usually not serious and requires further testing. Down’s screening is a mid-trimester screening test for the occurrence of aneuploid chromosome disorders in the fetus and is indicated for low-risk individuals, to be performed at 15 to 20 weeks of gestation. When the result suggests Down syndrome 21-trisomy 1:380, it indicates a critical risk, which is usually not serious and requires non-invasive prenatal testing (NIPT) as prescribed by the doctor to further screen and rule out the risk of developing the disease. NIPT is suitable for secondary screening of high-risk groups, such as Down’s critical risk, etc. The detection rate of NIPT for trisomy 21 is 99%, so NIPT can be performed to rule out the risk of morbidity when Down’s critical risk is present. However, for pregnant women with their own chromosomal abnormalities or genetic disorders and special cases such as fetal structural malformations, NIPT cannot be used and prenatal diagnosis is required.