1. Department of Obstetrics and Gynecology, Uijeongbu St. Mary's Hospital, The Catholic University of Korea College of Medicine, Uijeongbu, Korea.
2. Department of Pathology, The Catholic University of Korea College of Medicine, Seoul, Korea.
3. Department of Obstetrics and Gynecology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Korea.