1. Akita University Graduate School of Medicine Department of Obstetrics and Gynaecology, , 1-1-1, Hondo, Akita-shi, Akita 010-8543, Japan
2. Hokkaido University Department of Public Health, Faculty of Medicine, , Kita 15, Nishi 7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan
3. Specified Non-profit Corporation FORECIA , Yamani Building 6F, 2-2-23, Nakadori, Akita-shi, Akita 010-0001, Japan
4. Umegaoka Women’s Clinic , Tokyo, 1-33-3, Umegaoka, Setagaya-ku, Tokyo 154-0022, Japan
5. Akita University School of Medicine , Department of Medicine, 1-1-1, Hondo, Akita-shi, Akita 010-8543, Japan