1. Department of Epidemiology, Rollins School of Public Health Emory University Atlanta Georgia USA
2. National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention Atlanta Georgia USA
3. Department of Pediatrics and Epidemiology University of Florida College of Medicine and College of Public Health and Health Professions Gainesville Florida USA
4. School of Community Health Sciences University of Nevada Reno Reno Nevada USA