Department of Epidemiology and Health Statistics,School of public health,Ningxia Medical University,Yinchuan 750004,Ningxia,China
Department of Pediatric Surgery,Peking University First Hospital Ningxia Women and Children's Hospital(Ningxia Hui Autonomous Region Maternal and Child Health Hospital,China),Yinchuan 750004,Ningxia,China
Key Laboratory of Environmental Factors and Chronic Disease Control,Ningxia Medical University,Yinchuan 750004,Ningxia,China