This Practice Bulletin was developed by the American College of obstetricians andGynecologists’Committee on Practice Bulletins—Obstetrics and Committee on Genetics, and the Society for Maternal-Fetal Medicine in collaborationwithNancy C. Rose,MD, and Anjali J.Kaimal, MD, MAS, with the assistance of Lorraine Dugoff, MD, and Mary E. Norton, MD, on behalf of the Society for Maternal-Fetal Medicine.