1. Department of Obstetrics and Gynecology, Soonchunhyang University Cheonan Hospital, Cheonan, Korea.
2. Department of Pathology, Soonchunhyang University Cheonan Hospital, Cheonan, Korea.
3. Department of Obstetrics and Gynecology, Soonchunhyang University Bucheon Hospital, Soonchunhyang University College of Medicine, Bucheon, Korea.