1. Perinatal Clinical Trials Research Center, The Children's Hospital, Aurora, Colorado
2. Regional Obstetric Consultants, Jacksonville, Florida
3. Department of Obstetrics and Gynecology, Intermountain Salt Lake Clinic, Salt Lake City, Utah
4. Department of Pediatrics, University of Colorado Denver, Aurora, Colorado
5. Department of Obstetrics and Gynecology, Denver Health Medical Center, Denver, Colorado
6. Division of Maternal and Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama, Birmingham School of Medicine, Birmingham, Alabama