1. Department of Obstetrics and Gynecology, School of Medicine (A.J.P., A.A., N.S.), Aurora, Colorado 80045
2. Department of Biostatistics and Informatics, School of Public Health (A.A.), University of Colorado Denver, Aurora, Colorado 80045
3. Department of Epidemiology, Preventive, and Behavioral Medicine (S.L.C.), University of Massachusetts Medical School, Worcester, Massachusetts 01655
4. School of Public Health (S.D.H.), University of Michigan, Ann Arbor, Michigan 48109
5. Department of Community Health (N.K.), Boonshoft School of Medicine, Wright State University, Dayton, Ohio 45420
6. Department of Obstetrics and Gynecology (R.S.L.), Penn State College of Medicine, Hershey, Pennsylvania 17033