1. Department of Obstetrics and Gynecology, Division of Maternal Fetal Medicine, the George Washington University School of Medicine and Health Sciences, Washington, DC, USA;
2. Department of Obstetrics and Gynecology, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA, USA;
3. Department of Obstetrics and Gynecology, Division of Maternal Fetal Medicine, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA, USA