1. Division of Perinatology, Oregon Health & Sciences University, Portland, Oregon
2. Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, Michigan
3. Division of Maternal Fetal Medicine, University of Washington Medical Center, Seattle, Washington
4. Division of Maternal Fetal Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania
5. Division of Maternal Fetal Medicine, University of Texas Southwestern, Dallas, Texas