1. Department of Obstetrics and Gynecology and Ewha Medical Research Institute, College of Medicine Ewha Womans University Seoul Korea
2. Department of Obstetrics and Gynecology, Samsung Medical Center Sungkyunkwan University School of Medicine Seoul Korea
3. Department of Obstetrics and Gynecology, Konkuk University Medical Center Konkuk University School of Medicine Seoul Korea
4. Department of Obstetrics and Gynecology, College of Medicine The Catholic University of Korea Seoul Korea
5. Department of Obstetrics and Gynecology Seoul National University College of Medicine Seoul Korea