[1] Niigata Univ, Obstet & Gynecol, Niigata, Japan
[2] Osaka Univ, Obstet & Gynecol, Osaka, Japan
[3] Yokohama City Univ, Obstet & Gynecol, Yokohama, Kanagawa, Japan
[4] Saga Univ, Prevent Med, Saga, Japan
[5] Hokkaido Univ, Womens Hlth Med, Sapporo, Hokkaido, Japan