1. Department of Pediatrics, Boston University School of Medicine, Boston, Massachusetts;
2. Department of Pediatrics, Boston Medical Center, Boston, Massachusetts;
3. Data Coordinating Center, Boston University School of Public Health, Boston, Massachusetts;
4. Hennepin County Medical Center, Minneapolis, Minnesota;
5. Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland;
6. Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas; and
7. Department of Community Health Prevention, Drexel University School of Public Health, Philadelphia, Pennsylvania