1. Division of Gynecology, Department of Obstetrics and Gynecology, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8503, Japan and
2. Department of Obstetrics and Gynecology, Matsue City Hospital, Matsue 690-8509, Japan and
3. Department of Obstetrics and Gynecology, Tottori Prefectural Central Hospital, Tottori 680-0901, Japan