[1] Hokkaido Univ, Grad Sch Med, Dept Reprod & Dev Med, 7 Nishi,15 Kita,Kita Ku, Sapporo, Hokkaido, Japan
[2] Univ Yamanashi, Dept Epidemiol & Environm Med, 1110 Shimokato, Chuo City, Yamanashi, Japan
[3] Japanese Red Cross Hokkaido Coll Nursing, Div Clin Med, 664-1 Akebono, Kitami City, Hokkaido, Japan
[4] Asahikawa Med Univ, Dept Paediat, 2-1-1-1 Midorigaoka Higashi, Asahikawa City, Hokkaido, Japan
[5] Univ Yamanashi, Dept Paediat, 1110 Shimokato, Chuo City, Yamanashi, Japan
[6] NHO Kofu Natl Hosp, Dept Paediat, 11-35 Tenjin, Kofu City, Yamanashi, Japan