1. Department of Pediatrics, Women and Infants' Hospital of Rhode Island, Providence, Rhode Island
2. Department of Pediatrics, University of Texas Medical School at Houston, Houston, Texas
3. Department of Pediatrics, Wayne State University, Detroit, Michigan
4. Department of Statistics and Epidemiology, RTI International, Research Triangle Park, North Carolina
5. Department of Pediatrics, Yale University, New Haven, Connecticut
6. Department of Pediatrics, Case Western University, Cleveland, Ohio
7. Department of Pediatrics, University of Cincinnati, Cincinnati, Ohio
8. Department of Pediatrics, Duke University, Durham, North Carolina
9. Department of Pediatrics, Wake Forest University, Winston-Salem, North Carolina
10. National Institute of Child Health and Human Development, Bethesda, Maryland