1. National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, Ohio, USA.
2. Department of Family Medicine and Community Health, Duke University, Durham, North Carolina, USA.
3. Congenital Malformations Registry, New York State Department of Health, Albany, New York, USA.
4. National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.