1. Department of Pediatrics, College of Medicine, University of Kentucky, Lexington, Kentucky;
2. RTI International, Research Triangle Park, North Carolina;
3. Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee;
4. Department of Pediatrics, University of Miami School of Medicine, Miami, Florida;
5. Department of Pediatrics, Wayne State University School of Medicine, Detroit, Michigan;
6. Department of Pediatrics, Brown University Medical School, Providence, Rhode Island; and
7. Eunice Kennedy Shriver National Institute of Child Health and Human Development, Rockville, Maryland