1. Research Department, American College of Obstetricians and Gynecologists, Washington, District of Columbia.
2. Smithsonian National Zoo and Conservation Biology Institute, Washington, District of Columbia.
3. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Geisinger, Danville, Pennsylvania.
4. Division of Research, Health Resources and Services Administration, Maternal and Child Health Bureau, Office of Epidemiology and Research, Rockville, Maryland.
5. Department of Obstetrics and Gynecology, University of Washington School of Medicine, Seattle, Washington.