1. Section of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of Chicago, Chicago, Illinois; Department of Obstetrics and Gynecology, University of Vermont College of Medicine, Fletcher Allen Health Care, Burgess 202, 111 Colchester Avenue, Burlington, VT 05401
2. Section of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of Chicago, Chicago, Illinois