1. Department of Obstetrics and Gynecology, George Washington University Biostatistics Center, Washington, District of Columbia
2. Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, Alabama
3. The Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland
4. Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas
5. Department of Obstetrics and Gynecology, University of Utah, Salt Lake City, Utah
6. Department of Obstetrics and Gynecology, Case Western Reserve University-MetroHealth Medical Center, Cleveland, Ohio
7. Department of Obstetrics and Gynecology, The Ohio State University, Columbus, Ohio
8. Department of Obstetrics and Gynecology, Thomas Jefferson University and Drexel University, Philadelphia, Pennsylvania
9. Department of Obstetrics and Gynecology, Wayne State University, Detroit, Michigan
10. Department of Obstetrics and Gynecology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
11. Department of Obstetrics and Gynecology, University of Texas Health Science Center at Houston-Children's Memorial Hermann Hospital, Houston, Texas
12. Department of Obstetrics and Gynecology, Columbia University, New York, New York
13. Department of Obstetrics and Gynecology, University of Miami, Miami, Florida
14. Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Texas
15. Department of Obstetrics and Gynecology, University of Pittsburgh, Pittsburgh, Pennsylvania
16. Department of Obstetrics and Gynecology, NorthShore University Health System, Evanston, Illinois