1. Department of Obstetrics and Gynecology, Inha University Hospital, Inha University School of Medicine, Incheon, Korea.
2. Department of Obstetrics and Gynecology, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam, Korea.
3. Department of Obstetrics and Gynecology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea.