| Affiliation: | 1. Department of Obstetrics and Gynecology , University of North Carolina School of Medicine , Chapel Hill , North Carolina , USA;2. Department of Obstetrics and Gynecology , Boston University School of Medicine , Boston , Massachusetts , USA;3. Department of Obstetrics, Gynecology and Reproductive Sciences , University of Texas Medical School , Houston , Texas , USA;4. Department of Obstetrics and Gynecology, Perelman School of Medicine , University of Pennsylvania , Philadelphia , Pennsylvania , USA |
