1. Department of Obstetrics and Gynecology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Kyungpook National University Medical Center, Kyungpook National University School of Medicine, Daegu, Korea.
4. Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
5. Department of Obstetrics and Gynecology, St. Vincent’s Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea.
6. Department of Obstetrics and Gynecology, Hanyang University Medical Center, Seoul, Korea.
7. Department of Obstetrics and Gynecology, CHA Gangnam Medical Center, CHA University, Seoul, Korea.
8. Department of Obstetrics and Gynecology, Keimyung University School of Medicine, Daegu, Korea.
9. Department of Obstetrics and Gynecology, Ewha Womans University School of Medicine, Seoul, Korea.
10. Department of Obstetrics and Gynecology, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
11. Department of Obstetrics and Gynecology, Cheil General Hospital & Women’s Healthcare Center, Dankook University College of Medicine, Seoul, Korea.
12. Department of Obstetrics and Gynecology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
13. Department of Obstetrics and Gynecology, Sanggye Paik Hospital, Inje University, Seoul, Korea.
14. Department of Obstetrics and Gynecology, Ajou University School of Medicine, Suwon, Korea.
15. Department of Preventive Medicine, Korea University College of Medicine, Seoul, Korea.
16. Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
17. Department of Obstetrics and Gynecology, Seoul National University Hospital, Seoul, Korea.