1. Department of Obstetrics and Gynecology, Korea University College of Medicine, Korea University Anam Hospital, Seoul 02841, Republic of Korea
2. Department of Obstetrics and Gynecology, Korea University College of Medicine, Korea University Guro Hospital, Seoul 08308, Republic of Korea
3. Department of Obstetrics and Gynecology, Korea University College of Medicine, Korea University Ansan Hospital, Ansan 15355, Republic of Korea