1. National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, MD, USA
2. Department of Health and Human Services, United States Public Health Service, Washington, DC, USA
3. Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh Medical Center Magee-Womens Hospital, Pittsburgh, PA, USA
4. Department of Pediatrics, University of Pittsburgh Medical Center Children’s Hospital of Pittsburgh, Pittsburgh, PA, USA
5. Health Sciences Program, Argosy University, Arlington, VA, USA
6. School of Health Professions, Shenandoah University, Winchester, VA, USA