[1] Hamamatsu Univ, Sch Med, Dept Obstet & Gynecol Gynecol & Family Med, Hamamatsu, Shizuoka, Japan
[2] Jichi Med Univ, Dept Obstet & Gynecol, Shimotsuke, Japan
[3] Kitasato Med Univ, Sch Med, Dept Anesthesiol, Sagamihara, Kanagawa, Japan
[4] Nagoya City West Med Ctr, Dept Obstet & Gynecol, Nagoya, Aichi, Japan
[5] Osaka City Gen Hosp, Dept Obstet & Gynecol, Osaka, Japan
[6] Yotsuba Womens Clin, Takamatsu, Kagawa, Japan
[7] Saitama Med Ctr, Dept Obstet & Gynecol, Omiya, Saitama, Japan