1 Department of Obstetrics and Gynecology, Faculty of Medicine, Yamagata University, Iida-nishi, 2-2-2, Yamagata, 990-9585, Japan. m.fukase3@gmail.com.
2 Department of Obstetrics and Gynecology, Faculty of Medicine, Yamagata University, Iida-nishi, 2-2-2, Yamagata, 990-9585, Japan.