A blood test can be performed between the 15th and 22nd weeks of the pregnancy to determine whether the baby is at risk for certain birth defects. Blood is drawn from a vein and the sample is sent to a laboratory for testing. If the test is abnormal other tests can be performed to rule out birth defects.
Update Date 4/5/2016
Updated by: Irina Burd, MD, PhD, Associate Professor of Gynecology and Obstetrics at Johns Hopkins University School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.