[1] Southern Med Univ, Affiliated Hosp 7, Dept Nursing, 28 Liguan Rd, Lishui 528244, Foshan, Peoples R China
[2] Southern Med Univ, Affiliated Hosp 7, Dept Obstet & Gynecol, Foshan, Peoples R China
[3] Ottawa Hosp Res Inst, Clin Epidemiol Program, Ottawa, ON, Canada
[4] Guangdong Med Univ, Affiliated Hosp, Dept Nursing, Zhanjiang, Peoples R China
[5] Univ Ottawa, Fac Med, Dept Obstet & Gynecol, Ottawa, ON, Canada
[6] Univ Ottawa, Sch Epidemiol & Publ Hlth, Fac Med, Ottawa, ON, Canada