1. Department of Obstetrics and Gynecology, Miz Womens's Hospital, Daejeon, Korea.
2. Department of Obstetrics and Gynecology, Bucheon St. Mary's Hospital, The Catholic University College of Medicine, Bucheon, Korea.
3. Department of Obstetrics and Gynecology, Incheon Seoul Women's Hospital, Incheon, Korea.
4. Department of Obstetrics and Gynecology, Chosun University College of Medicine, Gwangju, Korea.