1. Department of Obstetrics and Gynecology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
2. Department of Obstetrics and Gynecology, Tokyo Medical University Ibaraki Medical Center, Ami, Japan
3. Department of Obstetrics and Gynecology, Iwate Medical University School of Medicine, Yahaba, Japan
4. Department of Obstetrics and Gynecology, Fukushima Medical University School of Medicine, Fukushima, Japan
5. Department of Obstetrics and Gynecology, Hokkaido University School of Medicine, Sapporo, Japan
6. Department of Obstetrics and Gynecology, Akita University Graduate School of Medicine, Akita, Japan
7. Department of Obstetrics and Gynecology, Tohoku University Graduate Schoool of Medicine, Sendai, Japan
8. Department of Obstetrics and Gynecology, Yamagata University Faculty of Medicine, Yamagata, Japan
9. Division of Obstetrics and Gynecology, Tohoku Medical and Pharmaceutical University Faculty of Medicine, Sendai, Japan
10. Department of Gynecology, Miyagi Cancer Center, Natori, Japan