1. Division of Population Health Sciences, University of Alaska, Anchorage, AK 99508, USA
2. Department of Obstetrics and Gynecology, Augusta University, Augusta, GA 30912, USA
3. Department of Obstetrics and Gynecology, University of Oklahoma College of Medicine, Oklahoma City, OK 73104, USA
4. Department of Obstetrics and Gynecology, University of North Carolina, Chapel Hill, NC 27599, USA
5. Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California San Francisco, San Francisco, CA 94143, USA
6. Department of Obstetrics and Gynecology, Pennsylvania State University, Hershey, PA 16802, USA
7. Department of Obstetrics and Gynecology, Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI 48202, USA
8. Department of Obstetrics and Gynecology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
9. Department of Biostatistics, Yale University School of Public Health, New Haven, CT 06520, USA
10. Department of Obstetrics and Gynecology, University of Colorado, Denver, CO 80204, USA