[1] Chongqing Hlth Ctr Women & Children, Dept Obstet & Gynecol, Chongqing, Peoples R China
[2] Chongqing Med Univ, Women & Childrens Hosp, Dept Obstet & Gynecol, Chongqing, Peoples R China
[3] Natl Key Clin Special Construction Project Obstetr, Chongqing, Peoples R China
[4] Chongqing Res Ctr Prevent & Control Maternal & Chi, Chongqing, Peoples R China
[5] 120 Longshan Rd, Chongqing 401147, Peoples R China