V Berghella1, L Dugoff2, J Ludmir1. 1. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Sidney Kimmel Medical College of Thomas Jefferson University, 833 Chestnut Street, First Floor, Philadelphia, PA 19107, USA. 2. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia, PA, USA.