A high risk of Down syndrome should be diagnosed prenatally with a noninvasive DNA or amniocentesis test.
Pregnant women are usually screened for Down syndrome after the 12th week of pregnancy. The risk factor of the fetus suffering from congenital anomalies and neural tube defects is determined by testing the pregnant woman’s blood for alpha-fetoprotein, chorionic gonadotropin, and free estriol, and by combining this with the woman’s own condition.
The accuracy rate of Down’s screening is between 60-75%, with a false-positive rate of 5% or more. If the Down syndrome is high risk, pregnant women need to do amniocentesis non-invasive DNA testing or amniocentesis at 16-22 weeks of gestation to rule out chromosomal abnormalities, high risk of open neural tube defects, and to reduce the chances of false positives in Down screening.
If the results of the prenatal diagnosis are high risk or chromosomal abnormalities are found, continuation of the pregnancy is not recommended.