1. Department of Obstetrics and Gynecology, Institute of Women’s Life Medical Science, Yonsei University College of Medicine, Seoul, Korea.
2. Department of Obstetrics and Gynecology, Asan Medical Center, Ulsan University Medical School, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Korea University Guro Hospital, Korea University College of Medicine, Seoul, Korea.
4. Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea.
5. Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.