[Xie, Ri-Hua] Huaihua Med Coll, Changsha, Hunan, Peoples R China.
[Wen, Shi Wu] Univ Ottawa, Dept Obstet & Gynecol, OMNI Res Grp, Fac Med, Ottawa, ON K1H 8L6, Canada.
[Walker, Mark; Xie, Ri-Hua; Yang, Jianzhou; Wen, Shi Wu] Univ Ottawa, Clin Epidemiol Program, Ottawa Hosp Res Inst, Ottawa, ON K1H 8L6, Canada.
[Yang, Jianzhou] Univ Ottawa, Inst Populat Hlth, McLaughlin Ctr Populat Hlth Risk Assessment, Ottawa, ON K1H 8L6, Canada.
[Yang, Jianzhou] Changzhi Med Coll, Dept Prevent Med, Changsha, Hunan, Peoples R China.