[1] Hokkaido Univ, Grad Sch Med, Dept Obstet & Gynecol, Kita Ku, N15 W7, Sapporo, Hokkaido 0608638, Japan
[2] Saitama Med Univ, Dept Obstet & Gynecol, Ctr Maternal Fetal & Neonatal Med, Saitama Med Ctr, Kawagoe, Saitama, Japan
[3] Juntendo Univ, Urayasu Hosp, Dept Obstet & Gynecol, Chiba, Japan
[4] Aiiku Hosp, Aiiku Maternal & Child Hlth Ctr, Dept Obstet & Gynecol, Tokyo, Japan
[5] Tokyo Metropolitan Bokutoh Hosp, Dept Obstet & Gynecol, Tokyo, Japan
[6] Mie Univ, Grad Sch Med, Dept Obstet & Gynecol, Tsu, Mie, Japan
[7] Hamamatsu Med Ctr, Dept Obstet & Gynecol, Hamamatsu, Shizuoka, Japan
[8] Juntendo Univ, Grad Sch Med, Dept Obstet & Gynecol, Tokyo, Japan
[9] Japan Soc Obstet Gynecol & Neonatal Hematol, Kitakyushu, Fukuoka, Japan