1. Department of Pediatrics, University of Iowa, Iowa City, Iowa;
2. Social, Statistical and Environmental Sciences Unit, RTI International, Research Triangle Park, North Carolina;
3. Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas;
4. Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut;
5. Department of Pediatrics, University of Texas Medical School at Houston, Houston, Texas;
6. Department of Pediatrics, Rainbow Babies & Children's Hospital and Case Western Reserve University, Cleveland, Ohio;
7. Department of Pediatrics, Wayne State University, Detroit, Michigan;
8. Department of Pediatrics, Emory University School of Medicine and Children's Healthcare of Atlanta, Atlanta, Georgia;
9. Mercy Medical Center, Des Moines, Iowa;
10. Social, Statistical and Environmental Sciences Unit, RTI International, Rockville, Maryland;
11. Department of Pediatrics, Women & Infants Hospital of Rhode Island and Brown University, Providence, Rhode Island;
12. Department of Pediatrics, Duke University, Durham, North Carolina;
13. Department of Pediatrics, Stanford University School of Medicine and Lucile Packard Children's Hospital, Palo Alto, California;
14. Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama;
15. Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana;
16. Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah;
17. Department of Pediatrics, University of New Mexico Health Sciences Center, Albuquerque, New Mexico;
18. Center for Research, Education, and Quality, Pediatrix Medical Group, Sunrise, Florida; and
19. Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland