1. Department of Obstetrics and Gynecology, Osaka University Graduate School of Medicine , 2-2 Yamadaoka, Suita, Osaka 565-0871 , Japan
2. Department of Obstetrics and Gynecology, Osaka Rosai Hospital , 1179-3, Nakasone, Kita-ku, Sakai, Osaka 591-8025 , Japan
3. Department of Obstetrics and Gynecology, Faculty of Medicine, Oita University , Idaigaoka 1-1, Hasama-machi, Yufu, Oita 879-5593 , Japan