[1] Nippon Med Sch, Dept Obstet & Gynecol, Tokyo, Japan
[2] Osaka Univ, Dept Obstet & Gynecol, Osaka, Japan
[3] Kobe Univ, Dept Obstet & Gynecol, Grad Sch Med, Kobe, Japan
[4] Hakodate Municipal Hosp, Dept Obstet & Gynecol, Hokkaido, Japan
[5] Juntendo Univ, Dept Obstet & Gynecol, Tokyo, Japan
[6] Fujita Hlth Univ, Dept Obstet & Gynecol, Sch Med, Toyoake, Aichi, Japan
[7] Shin Yurigaoka Hosp, Dept Obstet & Gynecol, Kawasaki, Japan
[8] Ishikawa Prefectural Cent Hosp, Dept Obstet & Gynecol, Kanazawa, Japan
[9] Tokai Univ, Dept Obstet & Gynecol, Sch Med, Isehara, Japan
[10] Kyoto Univ, Dept Obstet & Gynecol, Kyoto, Japan
[11] Univ Tokyo, Dept Obstet & Gynecol, Tokyo, Japan
[12] Meirikai Tokyo Yamato Hosp, Tokyo, Japan