1. 1Department of Epidemiology, University of North Carolina at Chapel Hill Gillings School of Global Public Health, Chapel Hill, North Carolina.
2. 2Division of Reproductive Endocrinology and Infertility, Department of Obstetrics and Gynecology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina.
3. 3Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina.
4. 4Division of Research, Kaiser Permanente Northern California, Oakland, California.
5. 5Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California.
6. 6Atlantic Reproductive Medicine Associates, Raleigh, North Carolina.