1. Department of Obstetrics and Gynecology, University of Washington School of Medicine, Seattle, WA 98195, USA
2. Department of Obstetrics and Gynecology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53726, USA
3. Department of Research, American College of Obstetricians and Gynecologists, Washington, DC 20024, USA
4. Department of Global Health, University of Washington School of Medicine, Seattle, WA 981985, USA