[1] Guangzhou Med Univ, Guangzhou Med Ctr Crit Pregnant Women, Key Lab Major Obstetr Dis Guangdong Prov, Affiliated Hosp 3,Dept Obstet & Gynecol, Guangzhou, Guangdong, Peoples R China
[2] Univ Ottawa, Fac Med, Dept Obstet & Gynecol, OMNI Res Grp, Ottawa, ON, Canada
[3] Publ Hlth Agcy Canada, Ottawa, ON, Canada
[4] Ottawa Hosp, Res Inst, Clin Epidemiol Program, Ottawa, ON, Canada
[5] Univ Ottawa, Fac Med, Sch Epidemiol Publ Hlth & Prevent Med, Ottawa, ON, Canada