1. Department of Obstetrics & Gynecology University of North Carolina School of Medicine Chapel Hill NC USA
2. Department of Biostatistics Gillings School of Global Public Health University of North Carolina Chapel Hill NC USA
3. Departments of Public Health Sciences and Obstetrics & Gynecology University of Virginia School of Medicine Charlottesville VA USA
4. Department of Statistical Science and Duke Global Health Institute Duke University Durham NC USA
5. Departments of Epidemiology and Obstetrics and Gynecology Brown University Providence RI USA