1. Division of Birth Defects and Developmental Disabilities, National Center on Birth Defects and Developmental Disabilities, and
2. Division of Environmental Hazards & Health Effects, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia;
3. Research Triangle Institute International, Atlanta, Georgia;
4. Texas Department of State Health Services, Austin, Texas; and
5. Department of Medicine, University of Mississippi Medical Center, Jackson, Mississippi