[Walker, Mark; Xie, Haiyan; Xie, Ri-hua; Wen, Shi Wu] Univ Ottawa, OMNI Res Grp, Dept Obstet & Gynecol, Fac Med, Ottawa, ON K1H 8L6, Canada.
[Walker, Mark; Xie, Haiyan; Xie, Ri-hua; Wen, Shi Wu] Huaihua Med Coll, Dept Nursing, Huaihua, Peoples R China.
[Xie, Ri-hua] Ottawa Hosp Res Inst, Clin Epidemiol Program, Ottawa, ON, Canada.
[Lei, Jun] Cent S Univ, Xiang Ya Hosp 3, Changsha, Hunan, Peoples R China.
[Wang, Shuhong] Cent S Univ, Xiangya Hosp, Changsha, Hunan, Peoples R China.