1. Department of Biostatistics, School of Public Health, Nanjing Medical University, Nanjing, Jiangsu, P.R. China
2. NPFPC Contraceptive Adverse Reaction Surveillance Center, Jiangsu Institute of Planned Parenthood Research, Nanjing, Jiangsu, P.R. China
3. China International Cooperation Center of Environment and Human Health, Nanjing Medical University, Nanjing, Jiangsu, P.R. China