1 Department of Obstetrics and Gynecology, Kyungpook National University Chilgok Hospital, Kyungpook National University, School of Medicine, Daegu, Korea.
2 Department of Obstetrics and Gynecology, Kyungpook National University Chilgok Hospital, Kyungpook National University, School of Medicine, Daegu, Korea. wjseong@knu.ac.kr.