1. Department of Obstetrics and Gynecology, Yongin Severance Hospital, Yonsei University College of Medicine, Yongin, Korea.
2. Department of Obstetrics and Gynecology, Institute of Women's Medical Life Science, Yonsei Cancer Center, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Bucheon St. Mary's Hospital, the Catholic University College of Medicine, Bucheon, Korea.