Sichuan University - National Office for Maternal and Child Health Surveillance of China, Sichuan University - National Office for Maternal and Child Health Surveillance of China, Sichuan University - National Office for Maternal and Child Health Surveillance of China, Sichuan University - National Office for Maternal and Child Health Surveillance of China, Sichuan University - National Office for Maternal and Child Health Surveillance of China, Sichuan University - National Office for Maternal and Child Health Surveillance of China, Sichuan University - National Office for Maternal and Child Health Surveillance of China, Sichuan University - National Office for Maternal and Child Health Surveillance of China, Sichuan University - National Office for Maternal and Child Health Surveillance of China, Sichuan University - National Office for Maternal and Child Health Surveillance of China, Sichuan University - National Office for Maternal and Child Health Surveillance of China and Sichuan University, West China Second University Hospital - Department of Pediatrics