A high risk non-invasive low risk from Down’s screening may be due to a false positive from Down’s screening, and a low risk from a non-invasive DNA test result will prevail.
Both Down screening and non-invasive DNA are prenatal screening tests that screen fetuses for risk of trisomy 18, trisomy 13, and trisomy 21.
Both are non-invasive tests with a certain false-positive and false-negative rate, which can only detect the risk of the fetus being at risk for the disease, but cannot fully confirm the diagnosis, and an accurate diagnosis needs to be made by amniocentesis.
Noninvasive DNA is more accurate than Down screening, so if the Down screening is high risk but the noninvasive DNA indicates a low risk, you don’t need to worry too much.