1. Department of Neurology, School of Medicine and DentistryUniversity of RochesterRochester, Box 673, 601 Elmwood Avenue New York14642 USA
2. Colorado School of Public HealthUniversity of ColoradoAurora Colorado USA
3. New York State Department of HealthAlbany New York USA
4. Bureau of Environmental and Occupational Epidemiology, New York State Department of HealthAlbany New York USA
5. Congenital Malformations Registry, New York State Department of HealthAlbany New York USA