1. Department of Obstetrics and Gynecology, Tohoku University School of Medicine, Sendai, Japan.
2. Department of Obstetrics and Gynecology, Yamagata University Faculty of Medicine, Yamagata, Japan.
3. Department of Obstetrics and Gynecology, Tokai University School of Medicine, Isehara, Japan.
4. Department of Obstetrics and Gynecology, Kumamoto University Faculty of Life Sciences, Kumamoto, Japan.
5. Department of Obstetrics and Gynecology, Kawasaki Medical School, Kurashiki, Japan.
6. Clinical Research, Innovation and Education Center, Tohoku University Hospital, Sendai, Japan.
7. Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo, Japan.
8. Department of Obstetrics and Gynecology, Dokkyo Medical University, Tochigi, Japan.