1. From the Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, Texas; and Department of Obstetrics and Gynecology,
2. Brigham and Women's Hospital and
3. Massachusetts General Hospital, and
4. Joint Program in Neonatology (Brigham and Women's Hospital, Children's Hospital, Beth Israel Deaconess Medical Center), Harvard Medical School, and
5. Department of Epidemiology and Biostatistics, Boston University School of Public Health, Boston, Massachusetts.