About the Authors

Li Liu

Affiliation Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America

Mengying Li

Affiliation Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America

Li Yang

Affiliation Guangxi Medical University, School of Public Health, Nanning, China

Lirong Ju

Affiliation Capital Medical University, School of Public Health, Beijing, China

Biqin Tan

Affiliation Gongcheng County Maternal and Child Health Hospital, Gongcheng County, China

Neff Walker

Affiliation Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America

Jennifer Bryce

Affiliation Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America

Harry Campbell

Affiliation University of Edinburgh Medical School, Edinburgh, United Kingdom

Robert E. Black

Affiliation Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America

Yan Guo

guoyan@bjmu.edu.cn

Affiliation Peking University Health Science Center, School of Public Health, Beijing, China

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Interpretation of results and subsequent revision of the manuscript: LL ML LY LJ BT NW JB HC REB YG. Conceived and designed the experiments: LL NW JB HC RB YG ML. Performed the experiments: LL ML LJ LY BT YG. Analyzed the data: ML LL. Wrote the paper: LL ML.