Steven P. Shelov, MD, MS, FAAP, is chairman of pediatrics at Maimonides Medical Center and Lutheran Medical Center, a professor of pediatrics at Mount Sinai School of Medicine, and vice president of the Infants' and Children's Hospital of Brooklyn. He has edited several books from the American Academy of Pediatrics. M. Rosario Gonzalez de Rivas, MD, is a professor in pediatrics at the University of Puerto Rico School of Medicine.