1. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina;
2. Birth Defects Monitoring Branch, and
3. Division of Pediatric Cardiology, Children’s Healthcare of Atlanta, Atlanta, Georgia; and
4. Department of Pediatrics, School of Medicine, Emory University, Atlanta, Georgia
5. Health and Spatial Analysis Branch, State Center for Health Statistics, Division of Public Health, North Carolina Department of Health and Human Services, Raleigh, North Carolina;