1. Biostatistics Center, George Washington University, Washington, District of Columbia
2. Department of Obstetrics and Gynecology, University of Utah Health Sciences Center, Salt Lake City, Utah
3. Department of Obstetrics and Gynecology, Northwestern University, Chicago, Illinois
4. Department of Obstetrics and Gynecology, University of North Carolina, Chapel Hill, North Carolina
5. Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Texas
6. Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland
7. Department of Obstetrics and Gynecology, University of Pittsburgh, Pittsburgh, Pennsylvania
8. Department of Obstetrics and Gynecology, Brown University, Providence, Rhode Island
9. Department of Obstetrics and Gynecology, Children's Memorial Hermann Hospital, University of Texas Health Science Center at Houston, Houston, Texas
10. Department of Obstetrics and Gynecology, Columbia University, New York, New York
11. Department of Obstetrics and Gynecology, MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio
12. Department of Obstetrics and Gynecology, The Ohio State University, Columbus, Ohio
13. Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia, Pennsylvania
14. Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, Alabama