1. Emory University School of Medicine, Department of Pediatrics, and Children's Healthcare of Atlanta, Atlanta, Georgia;
2. Statistics and Epidemiology Unit, RTI International, Research Triangle Park, North Carolina;
3. Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas;
4. Department of Pediatrics, Division of Neonatology, University of Utah School of Medicine, Salt Lake City, Utah;
5. Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana;
6. Division of Neonatology, Stanford University Medical Center, Palo Alto, California;
7. Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut;
8. Department of Pediatrics, Duke University, Durham, North Carolina;
9. Department of Pediatrics, Tufts Medical Center, Floating Hospital for Children, Tufts Medical Center, Boston, Massachusetts;
10. Department of Pediatrics, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, Georgia;
11. Department of Pediatrics, Wayne State University, Detroit, Michigan;
12. Department of Pediatrics, University of Texas Medical School at Houston, Texas;
13. Division of Neonatology, University of Alabama at Birmingham, Birmingham, Alabama;
14. Department of Pediatrics, University of New Mexico Health Sciences Center, Albuquerque, New Mexico;
15. Department of Pediatrics, University of Iowa, Iowa City, Iowa;
16. Department of Pediatrics, Rainbow Babies & Children's Hospital, Case Western Reserve University, Cleveland, Ohio;
17. Department of Pediatrics, University of Cincinnati, Ohio;
18. Department of Pediatrics, Women & Infants Hospital, Brown University, Providence, Rhode Island;
19. Centers for Disease Control and Prevention, Atlanta, Georgia;
20. Statistics and Epidemiology Unit, RTI International, Rockville, Maryland;
21. Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland