Peking University - Department of Epidemiology and Biostatistics, Peking University - Institute of Reproductive and Child Health, Chinese Center for Disease Control and Prevention (China CDC) - National Center for Women and Children's Health, Chinese Center for Disease Control and Prevention - National Center for Women and Children's Health, Peking University - Department of Epidemiology and Biostatistics, Haidian Maternal & Child Health Hospital - Department of Obstetrics and Gynecology, Haidian Maternal & Child Health Hospital - Department of Obstetrics and Gynecology, Peking University - Department of Epidemiology and Biostatistics, Peking University - Department of Epidemiology and Biostatistics, Peking University - Department of Epidemiology and Biostatistics, Peking University - Department of Epidemiology and Biostatistics, Peking University - Department of Epidemiology and Biostatistics, Peking University - Department of Epidemiology and Biostatistics, Peking University - Department of Epidemiology and Biostatistics, Peking University - College of Urban and Environmental Sciences, Chinese Academy of Sciences (CAS) - Institute of Geographic Sciences and Natural Resources Research, Duke University - Department of Obstetrics and Gynecology, Peking University - Department of Epidemiology and Biostatistics, Chinese Center for Disease Control and Prevention (China CDC) - National Center for Women and Children's Health, Haidian Maternal & Child Health Hospital - Department of Obstetrics and Gynecology and Peking University - Institute of Reproductive and Child Health