1. Department of Obstetrics and Gynecology; St. Marianna University School of Medicine; Kawasaki Kanagawa Japan
2. Department of Obstetrics and Gynecology; Mie University School of Medicine; Tsu Mie Japan
3. Department of Obstetrics and Gynecology; Sakakibara Heart Institute; Tokyo Japan
4. Department of Obstetrics and Gynecology; Showa University School of Medicine; Tokyo Japan
5. Ishiwata Obstetrics and Gynecology Hospital; Mito Ibaraki Japan