1. Department of Epidemiology; Graduate School of Public Health; University of Pittsburgh; Pittsburgh Pennsylvania USA
2. Department of Obstetrics, Gynecology, and Reproductive Sciences; School of Medicine; University of Pittsburgh; Pittsburgh Pennsylvania USA
3. Magee-Womens Research Institute; Pittsburgh Pennsylvania USA
4. Division of Epidemiology; School of Public Health; University of California at Berkeley; Berkeley California USA
5. Department of Epidemiology; Rollins School of Public Health; Emory University; Atlanta Georgia USA