1. Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
2. Biostatistical Collaboration Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
3. Department of Obstetrics & Gynecology, John H. Stroger, Jr. Hospital of Cook County, Cook County Health, Chicago, Illinois
4. Department of Anthropology, The Graduate School, Northwestern University, Evanston, Illinois