1. Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo, Japan.
2. Department of Obstetrics and Gynecology, Faculty of medicine, Yamagata University, Yamagata, Japan.
3. Department of Information Science, Center for Liberal Arts and Sciences, Iwate Medical University, Morioka, Japan.
4. Department of Obstetrics and Gynecology, Wakayama Medical University, Wakayama, Japan.
5. Department of Obstetrics and Gynecology, Steel Memorial Yahata Hospital, Kitakyushu, Japan.
6. Department of Obstetrics and Gynecology, Tokai University School of Medicine, Tokyo, Japan.
7. Department of Obstetrics and Gynecology, School of medicine, Niigata University, Niigata, Japan.
8. Department of Obstetrics and Gynecology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.