1. Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, British Columbia, Canada; Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, California
2. Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, California; Department of Obstetrics and Gynecology, University of British Columbia, B.C. Women's Hospital, Rm. 2H30, 4490 Oak Street, Vancouver B.C., V6H 3V5, Canada