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 - Department of Pediatrics