[1] Tohoku Univ, Dept Obstet & Gynecol, Sch Med, Sendai, Japan
[2] Hokkaido Univ, Dept Obstet & Gynecol, Sch Med, Sapporo, Japan
[3] Kobe Univ, Dept Obstet & Gynecol, Grad Sch Med, Kobe, Japan
[4] Kyorin Univ, Dept Obstet & Gynecol, Fac Med, Mitaka, Japan
[5] Iwate Med Univ, Dept Obstet & Gynecol, Shiwa, Japan
[6] Yamagata Univ, Dept Obstet & Gynecol, Fac Med, Yamagata, Japan
[7] Tohoku Univ, Dept Obstet & Gynecol, Sch Med, Seiryo Machi,Aoba Ku, Sendai, Miyagi 9808574, Japan