Down screening for trisomy 21 in mid-pregnancy reveals a high risk and requires a non-invasive DNA test for clarification and consideration of termination of pregnancy if necessary. Down screening refers to screening for Down syndrome, a chromosomal abnormality in which the fetus will have significant developmental abnormalities. When Down syndrome screening is found to be high risk, the next step in the process is a non-invasive DNA test to determine whether there is a chromosomal abnormality, and if the result is still abnormal, termination of pregnancy should be considered. When the risk of Down syndrome screening is high, it is recommended to go to the hospital in time and take the next step under the doctor’s guidance to clearly diagnose whether it belongs to the real trisomy 21 or not.