1. Harvard Newborn Medicine Program, Children's Hospital Boston and Beth Israel Deaconess Medical Center, Boston, Massachusetts
2. Section of Neonatology, Department of Pediatrics, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas
3. Division of Health Policy and Quality, Houston Center for Quality of Care and Utilization Studies, Michael E. DeBakey Veteran's Administration Medical Center, Houston, Texas
4. Department of Society, Human Development and Health, Harvard School of Public Health, Boston, Massachusetts
5. Perinatal Research Unit, Kaiser Permanente Medical Care Program, Oakland, California
6. School of Public Health, University of Michigan, Ann Arbor, Michigan