1. Department of Obstetrics and Gynecology, Research Institute of Medical Science, Konkuk University School of Medicine, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
4. Department of Obstetrics and Gynecology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
5. Department of Obstetrics and Gynecology, Seoul National University Hospital, Seoul, Korea.
6. Department of Obstetrics and Gynecology, Inje University Sanggye Paik Hospital, Seoul, Korea.
7. Department of Obstetrics and Gynecology, Research Institute of Medical Science, Soonchunhyang University Cheonan Hospital, Cheonan, Korea.
8. Department of Obstetrics and Gynecology, Dongguk University College of Medicine, Goyang, Korea.
9. Department of Obstetrics and Gynecology, Ajou University School of Medicine, Suwon, Korea.
10. Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea.
11. Department of Obstetrics and Gynecology, Konyang University Hospital, Daejeon, Korea.
12. Department of Obstetrics and Gynecology, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
13. Department of Obstetrics and Gynecology, Medical School of Jeju National University, Jeju National University Hospital, Jeju, Korea.
14. Department of Obstetrics and Gynecology, Guro Hospital, Korea University College of Medicine, Seoul, Korea.