[1] Japan Council Qual Hlth Care, Publ Interest Inc Fdn, Dept Japan Obstet Compensat Syst Cerebral Palsy, Tokyo, Japan
[2] Showa Univ, Northern Yokohama Hosp, Dept Obstet & Gynecol, Yokohama, Kanagawa, Japan
[3] Univ Tokyo, Grad Sch Med, Dept Publ Hlth, Tokyo, Japan
[4] Miyazaki Univ, Dept Obstet & Gynecol, Fac Med, Miyazaki, Japan
[5] Oita Prefectural Hosp, Dept Obstet, Oita, Japan
[6] St Marianna Univ, Dept Obstet & Gynecol, Sch Med, Kawasaki, Kanagawa, Japan
[7] Mie Univ, Dept Obstet & Gynecol, Tsu, Mie, Japan
[8] Univ Tsukuba, Dept Hlth Serv Res, Fac Med, Tsukuba, Ibaraki, Japan
[9] Nippon Med Univ, Dept Obstet & Gynecol, Tokyo, Japan
[10] Fukushima Med Univ, Dept Obstet & Gynecol, Fukushima, Japan
[11] Maeda Obstet & Gynecol Clin, Yaizu, Japan
[12] Hamamatsu Univ Sch Med, Dept Obstet & Gynecol, Hamamatsu, Shizuoka, Japan
[13] Nagasaki Univ, Dept Obstet & Gynecol, Nagasaki, Japan
[14] Kugayama Hosp, Tokyo, Japan
[15] Juntendo Univ, Dept Obstet & Gynecol, Tokyo, Japan