1. Department of Obstetrics and Gynecology, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Kangwon National University, School of Medicine, Chuncheon, Korea.
3. Department of Obstetrics and Gynecology, Konyang University College of Medicine, Daejeon, Korea.
4. Institute of Health & Science, Gyeongsang National University School of Medicine, Jinju, Korea.
5. Department of Obstetrics and Gynecology, Kyung Hee University Medical Center, Kyung Hee University School of Medicine, Seoul, Korea.
6. Department of Obstetrics and Gynecology, Korea University College of Medicine, Seoul, Korea.
7. Department of Obstetrics and Gynecology, Eulji University College of Medicine, Daejeon, Korea.
8. Department of Obstetrics and Gynecology, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Seoul, Korea.
9. Department of Obstetrics and Gynecology, Bucheon St. Mary's Hospital, The Catholic University of Korea College of Medicine, Bucheon, Korea.
10. Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
11. Departments of Obstetrics and Gynecology and Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
12. Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea.
13. Department of Obstetrics and Gynecology, The Catholic University of Korea College of Medicine, Seoul, Korea.
14. Department of Obstetrics and Gynecology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
15. Department of Obstetrics and Gynecology, St. Vincent's Hospital, The Catholic University of Korea College of Medicine, Suwon, Korea.
16. Department of Obstetrics and Gynecology, Soonchunhyang University College of Medicine, Seoul, Korea.
17. Department of Obstetrics and Gynecology, Yonsei University Health System, Seoul, Korea.
18. Department of Obstetrics and Gynecology, Yeouido St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Korea.
19. Department of Obstetrics and Gynecology, Chonnam National University Medical School, Gwangju, Korea.
20. Department of Obstetrics and Gynecology, Cheil General Hospital and Women's Healthcare Center, Catholic Kwandong University College of Medicine, Seoul, Korea.
21. Department of Obstetrics and Gynecology, Dankook University College of Medicine, Cheonan, Korea.
22. Department of Obstetrics and Gynecology, Ewha Womans University School of Medicine, Seoul, Korea.