[1] Huazhong Univ Sci & Technol, Tongji Med Coll, Sch Publ Hlth, Dept Epidemiol & Biostat,Minist Educ,Key Lab Envir, Wuhan, Peoples R China
[2] Sichuan Univ, West China Univ Hosp 2, Sichuan Univ, Key Lab Birth Defects & Related Dis Women & Childr, Chengdu, Peoples R China
[3] Shuangliu Maternal & Child Hlth Hosp, Shuangliu Inst Womens & Childrens Hlth, Chengdu, Peoples R China
[4] Albert Einstein Coll Med, Dept Epidemiol & Populat Hlth, Bronx, NY USA
[5] Huazhong Univ Sci & Technol, Tongji Med Coll, Sch Publ Hlth, Dept Epidemiol & Biostat, 13 Hangkong Rd, Wuhan 430030, Peoples R China