1. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, Texas
2. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Wisconsin-Madison, Madison, Wisconsin
3. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Texas Physicians, Houston, Texas