[1] Shandong Univ, Sch Publ Hlth, Dept Maternal & Child Hlth Care, Jinan 250012, Peoples R China
[2] Jining Med Univ, Sch Publ Hlth, Jining 272067, Peoples R China
[3] Tulane Univ, Sch Publ Hlth & Trop Med, Hlth Sci Ctr, New Orleans, LA USA
[4] Chinese Ctr Dis Control & Prevent, Natl Ctr Publ Hlth Surveillance & Informat Serv, Beijing 100050, Peoples R China
[5] Univ Minnesota, Sch Publ Hlth, Div Epidemiol & Community Hlth, Minneapolis, MN 55455 USA