1. Department of Obstetrics and Gynecology; Kangbuk Samsung Hospital; Sungkyunkwan University School of Medicine; Seoul Korea
2. Department of Obstetrics and Gynecology; College of Medicine; Hanyang University; Seoul Korea
3. Department of Obstetrics and Gynecology; National Medical Center; Seoul Korea
4. Department of Obstetrics and Gynecology; MizMedi Hospital, Eulji University School of Medicine; Seoul Korea