1. Department of Epidemiology, Brown University School of Public Health, Providence, Rhode Island.
2. Division of Research, Women & Infants Hospital, Providence, Rhode Island.
3. Department of Obstetrics and Gynecology, Warren Alpert Medical School of Brown University, Providence, Rhode Island.
4. Department of Obstetrics and Gynaecology, University of British Columbia, Vancouver, Canada.
5. Center for Outcomes Research and Evaluation, Yale School of Medicine, New Haven, Connecticut.
6. United Health Group, Health Services Research, Boston, Massachusetts.
7. Department of Health Services, Policy, and Practice, Brown University School of Public Health, Providence, Rhode Island.
8. National Perinatal Information Center, Inc., Providence, Rhode Island.
9. Department of Pediatrics, Warren Alpert Medical School of Brown University, Providence, Rhode Island.