1. Department of Obstetrics and Gynecology, Howard University Hospital, Washington, District of Columbia
2. Center for Surgery and Public Health, Department of Surgery, Brigham and Women’s Hospital, Boston, Massachusetts
3. Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland
4. Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda, Maryland
5. Department of Obstetrics and Gynecology, Uniformed Services University of the Health Sciences, Bethesda, Maryland
6. Department of Obstetrics, Brigham and Women's Hospital, Boston, Massachusetts