1. The Department of Obstetrics and Gynecology, Northwestern University, Chicago, Illinois
2. The Ohio State University, Columbus, Ohio
3. Bethesda, Maryland
4. University of Alabama at Birmingham, Alabama
5. University of Texas Southwestern Medical Center, Dallas, Texas
6. University of Utah, Salt Lake City, Utah
7. Thomas Jefferson University, Philadelphia, Pennsylvania
8. Department of Obstetrics and Gynecology, Wayne State University, Detroit, Michigan
9. University of Miami, Miami, Florida
10. University of Tennessee, Memphis, Tennessee
11. University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
12. The University of Texas Health Science Center at Houston, Houston, Texas
13. Case Western Reserve University-MetroHealth Medical Center, Cleveland, Ohio
14. The George Washington University Biostatistics Center, Washington, District of Columbia