1. Department of Epidemiology, Gillings School of Global Public Health; University of North Carolina; Chapel Hill North Carolina
2. Department of Obstetrics & Gynecology; University of North Carolina School of Medicine; Chapel Hill North Carolina
3. Maternal and Child Health Bureau; Health Resources and Services Administration; Rockville Maryland
4. Department of Biostatistics, Gillings School of Global Public Health; University of North Carolina; Chapel Hill North Carolina
5. Department of Obstetrics and Gynecology; University of Tennessee Health Sciences Center College of Medicine; Nashville Tennessee
6. School of Nursing and Departments of Public Health Sciences and Obstetrics & Gynecology School of Medicine; University of Virginia; Charlottesville Virginia