1. Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, OR, USA;
2. Department of Obstetrics and Gynecology, University of Utah, Salt Lake City, UT, USA;
3. Department of Obstetrics, Gynecology and Reproductive Sciences, University of California San Francisco, San Francisco, CA, USA;
4. Department of Pediatrics, University of California San Francisco, San Francisco, CA, USA