1. Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
2. Department of Obstetrics and Gynecology, Washington University, St. Louis, Missouri
3. Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh Medical Center, Magee-Women's Hospital, Pittsburgh, Pennsylvania
4. Division of Newborn Medicine and Neonatal Intensive Care Unit, University of Mississippi Medical Center, Jackson, Mississippi
5. Department of Obstetrics and Gynecology, University of Texas Medical Branch at Galveston, Galveston, Texas