What is a prenatal screening test?

A prenatal screening test shows the risk for certain fetal conditions in pregnancy but cannot actually diagnose them. The conditions screened include Down syndrome, Trisomy 18 (a serious chromosome condition) and spina bifida. Information from screening tests is used to determine whether a diagnostic test, such as amniocentesis, is advised.

Each screening test requires a blood draw. Some also use a nuchal translucency (NT) ultrasound to measure the fluid at the back of the baby's neck. Screening tests do not increase the risk for miscarriage. Only one prenatal screening test is done during a pregnancy.