1. Department of Obstetrics and Gynecology, Dongguk University Ilsan Hospital, Goyang, Korea.
2. Department of Obstetrics and Gynecology, Cheil General Hospital and Women's Healthcare Center, Dankook University College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Ajou University Hospotal, Ajou University School of Medicine, Suwon, Korea.
4. Department of Obstetrics and Gynecology, Kyung Hee University Hospital at Gangdong, Kyung Hee University School of Medicine, Seoul, Korea.
5. Department of Obstetrics and Gynecology, Seoul National University Bundang Hospital, Seongnam, Korea.
6. Department of Obstetrics and Gynecology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
7. Department of Obstetrics and Gynecology, The Catholic University of Korea Incheon St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Korea.
8. Department of Obstetrics and Gynecology, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Korea.
9. Department of Obstetrics and Gynecology, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea.
10. Department of Obstetrics and Gynecology, Hamchoon Women's Clinic, Seoul, Korea.
11. Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.