Guided by ultrasound, your doctor pinpoints the spot where the umbilical cord meets the placenta. He then inserts a needle through your abdomen and uterus and into the umbilical cord and withdraws a small amount of fetal blood.
Review Date 5/16/2016
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.