Obstet Gynecol 2015 Jun;125(6):1321-1329
Department of Obstetrics and Gynecology, MedStar Washington Hospital Center/MedStar Georgetown University Hospital, and the Department of Obstetrics and Gynecology, Johns Hopkins Medicine at Sibley Memorial Hospital, Washington, DC; Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; and Research and Development, Sequenom Laboratories, San Diego, California.