1. Center for Health Care Research and Policy, Population Health Research Institute MetroHealth Medical System Cleveland Ohio USA
2. School of Medicine Case Western Reserve University Cleveland Ohio USA
3. Department of Epidemiology, Gillings School of Global Public Health University of North Carolina at Chapel Hill Chapel Hill North Carolina USA
4. Carolina Population Center University of North Carolina at Chapel Hill Chapel Hill North Carolina USA
5. Department of Obstetrics and Gynecology, Division of Maternal Fetal Medicine Warren Alpert Medical School of Brown University Providence Rhode Island USA
6. Department of Obstetrics and Gynecology University of Alabama at Birmingham Birmingham Alabama USA
7. Department of Obstetrics and Gynecology University of California San Francisco San Francisco California USA
8. Department of Obstetrics and Gynecology MetroHealth Medical System Cleveland Ohio USA
9. Department of Obstetrics and Gynecology University of North Carolina Chapel Hill North Carolina USA