1. Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, Changchun 130021, China
2. National Research Institute for Family Planning, Beijing 100081, China
3. Jilin Provincial Key Laboratory of Surgical Translational Medicine, China-Japan Union Hospital, Jilin University, Changchun 130033, China
4. Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06511, USA