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