Soochow University - Department of Epidemiology and Health Statistics, Huazhong University of Science and Technology - Maternal and Child Health Hospital of Hubei Province, Haidian Maternal & Child Health Hospital, Chinese Academy of Medical Sciences - National Research Institute for Family Planning, Soochow University - Department of Obstetrics and Gynecology, Maternal and Child Health Hospital of Hubei Province - Department of Obstetrics, Soochow University - Department of Epidemiology and Health Statistics, Haidian Maternal & Child Health Hospital, Women and Children Health Care Center of Taicang, Haidian Maternal & Child Health Hospital, Soochow University - Department of Epidemiology and Health Statistics, Haidian Maternal & Child Health Hospital, Soochow University - Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases and National Research Institute for Family Planning

Fudan University - Obstetrics & Gynecology Hospital, National Research Institute for Family Planning, Chinese Academy of Medical Sciences - National Research Institute for Family Planning, Fudan University - Obstetrics & Gynecology Hospital, National Research Institute for Family Planning, Government of the People's Republic of China - National Health and Family Planning Commission, Government of the People's Republic of China - National Health and Family Planning Commission, Government of the People's Republic of China - National Health and Family Planning Commission, Department of Maternal and Child Health, Government of the People's Republic of China - National Health and Family Planning Commission, Government of the People's Republic of China - National Health and Family Planning Commission, National Research Institute for Family Planning, National Research Institute for Family Planning, National Research Institute for Family Planning, National Research Institute for Family Planning, National Research Institute for Family Planning, Fudan University - Obstetrics & Gynecology Hospital and National Research Institute for Family Planning

Fudan University - Obstetrics and Gynecology Hospital, National Research Institute for Family Planning, National Research Institute for Family Planning, Fudan University - Obstetrics & Gynecology Hospital, National Research Institute for Family Planning, Government of the People's Republic of China - National Health and Family Planning Commission, Government of the People's Republic of China - National Health and Family Planning Commission, Government of the People's Republic of China - National Health and Family Planning Commission, Department of Maternal and Child Health, Government of the People's Republic of China - National Health and Family Planning Commission, Government of the People's Republic of China - National Health and Family Planning Commission, National Research Institute for Family Planning, National Research Institute for Family Planning, National Research Institute for Family Planning, National Research Institute for Family Planning, National Research Institute for Family Planning, Fudan University - Obstetrics & Gynecology Hospital and National Research Institute for Family Planning