[1] Sichuan Acad Med Sci, Dept Obstet & Gynecol, Chengdu 610072, Peoples R China
[2] Sichuan Prov Peoples Hosp, Chengdu 610072, Peoples R China
[3] Sichuan Prov Hosp Women & Children, Dept Obstet & Gynecol, Chengdu 610045, Peoples R China
[4] West China Second Univ Hosp, Dept Obstet & Gynecol, Chengdu 610041, Peoples R China
[5] Sichuan Univ, Minist Educ, Key Lab Birth Defects & Related Dis Women & Child, Chengdu 610041, Peoples R China