1. Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Seoul National University Hospital, Seoul, Korea.
3. Department of Obstetrics and Gynecology, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
4. Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
5. Department of Obstetrics and Gynecology, Ajou University Hospital, Ajou University School of Medicine, Suwon, Korea.
6. Department of Obstetrics and Gynecology, Yongin Severance Hospital, Yonsei University Medical College, Yongin, Korea.
7. Department of Obstetrics and Gynecology, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
8. Department of Obstetrics and Gynecology, Seoul Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
9. Department of Obstetrics and Gynecology, Eunpyung St. Mary’s Hospital, Catholic University Medical College, Seoul, Korea.