1. Department of Obstetrics and Gynecology, Northwestern University, Chicago, Illinois
2. Biostatistics Center, The George Washington University, Washington, District of Columbia
3. Department of Obstetrics and Gynecology, MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio
4. Department of Obstetrics and Gynecology, Columbia University, New York, New York
5. Department of Obstetrics and Gynecology, University of Utah Health Sciences Center, Salt Lake City, Utah
6. Department of Obstetrics and Gynecology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
7. Department of Obstetrics and Gynecology, UT Southwestern Medical Center, Dallas, Texas
8. Department of Obstetrics and Gynecology, University of Pittsburgh, Pittsburgh, Pennsylvania
9. Department of Obstetrics and Gynecology, The Ohio State University, Columbus, Ohio
10. Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, Alabama
11. Department of Obstetrics and Gynecology, The University of Texas Medical Branch, Galveston, Texas
12. Department of Obstetrics and Gynecology, Wayne State University, Detroit, Michigan
13. Department of Obstetrics and Gynecology, Brown University, Providence, Rhode Island
14. Department of Obstetrics and Gynecology, Children's Memorial Hermann Hospital, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, Texas
15. Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, Oregon