1. University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC.
2. University of North Carolina at Chapel Hill School of Public Health, Chapel Hill, NC.
3. Department of Obstetrics and Gynecology, University of North Carolina at Chapel Hill, Chapel Hill, NC.
4. Department of Obstetrics and Gynecology, University of Tennessee (UT), Graduate School of Medicine/UT Medical Center Knoxville, Knoxville, TN.