1. Department of Epidemiology; Graduate School of Public Health; University of Pittsburgh; Pittsburgh PA
2. Department of Obstetrics, Gynecology, and Reproductive Sciences; School of Medicine; University of Pittsburgh; Pittsburgh PA
3. Magee-Womens Research Institute; Pittsburgh PA
4. Department of Obstetrics & Gynaecology; University of British Columbia; Vancouver Canada
5. Division of Epidemiology; School of Public Health; University of California; Berkeley CA