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