[1] Sichuan Univ, West China Univ Hosp 2, Dept Obstet & Gynecol, Chengdu, Sichuan, Peoples R China
[2] Sichuan Univ, West China Univ Hosp 2, Key Lab Obstet & Gynecol & Pediat Dis & Birth Defe, Minist Educ, Chengdu, Sichuan, Peoples R China
[3] Sichuan Univ, West China Univ Hosp 2, Dept Pediat, Chengdu, Sichuan, Peoples R China
[4] Sichuan Univ, West China Hosp, Gen Practice Ward, Int Med Ctr Ward,Gen Practice Med Ctr, Chengdu, Sichuan, Peoples R China
[5] Sichuan Univ, Key Lab Obstet & Pediat Dis & Birth Defects, Dept Obstet & Gynecol, Minist Educ,West China Univ Hosp 2, Chengdu, Sichuan, Peoples R China