[1] Nihon Univ, Sch Med, Dept Obstet & Gynecol, Chiyoda City, Japan
[2] Nihon Univ, Sch Med, Dept Pathol & Microbiol, Div Microbiol, Chiyoda City, Japan
[3] Nihon Univ, Sch Med, Dept Obstet & Gynecol, 30-1 Oyaguchi Kamimachi, Tokyo, Tokyo 1738610, Japan