1. Department of Obstetrics and Gynecology Jichi Medical University Tochigi Japan
2. Center for Reproductive Medicine and Endoscopy, Sugiyama Clinic Marunouchi Tokyo Japan
3. Department of Obstetrics and Gynecology Akita University Graduate School of Medicine Akita Japan
4. Department of Obstetrics and Gynecology Graduate School of Medicine, The University of Tokyo Tokyo Japan
5. Department of Obstetrics and Gynecology Keio University School of Medicine Tokyo Japan