About the Authors
Division of Maternal and Child Health, School of Public Health, Peking University Beijing, Beijing, China
Department of Reproductive Health and Research, World Health Organization, Geneva, Switzerland
School of Public Health, Kunming Medical College, Kunming, Yunnan, China
Women’s Healthcare Section, Zhengzhou University 3rd Affiliated Hospital Zhengzhou, Henan, China
Hebei Women and Children Health Center, Shijiazhuang, Hebei, China
The authors have declared that no competing interests exist.
Conceived and designed the experiments: YW DH HJW HZ FY. Performed the experiments: YW HJW HZ FY YL FZY JHL WLC MLY. Analyzed the data: FY HJW. Contributed reagents/materials/analysis tools: HZ YL FZY JHL WLC MLY. Wrote the paper: FY HJW YW DH.