1. Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, CA, USA
2. Quantitative Sciences Unit, Stanford University School of Medicine, Stanford, CA, USA
3. Center for Health Research, Kaiser Permanente Center for Health Research NW, Portland, CA, USA
4. Department of Reproductive Medicine, Henry Ford Health System, Detroit, MI, USA
5. Department of Preventive Medicine, Feinberg School of Medicine at Northwestern, Chicago, IL, USA
6. Cleveland, OH, USA
7. Stanford Prevention Research Center, Stanford University School of Medicine, Stanford, CA, USA