1. George Washington University, Departments of Health Policy, Epidemiology, and Biostatistics, Rockville, Maryland.
2. National Institutes of Health Clinical Center, Department of Bioethics, Bethesda, Maryland.
3. Eunice Kennedy Shriver National Institute of Child Health and Human Development, Pregnancy and Perinatology Branch, Bethesda, Maryland.
4. National Institutes of Health, Office of Research on Women's Health, Bethesda, Maryland.