1. Department of Gastroenterology, The First Affiliated Hospital, Chongqing Medical University, Chongqing 400016, P.R. China
2. Department of Gastroenterology, Chongqing People's Hospital, Chongqing 400016, P.R. China
3. Chongqing Health Service Center, Chongqing 400000, P.R. China
4. Key Laboratory of Birth Defects and Reproductive Health, Chongqing Population and Family Planning of Chongqing Science and Technology Research Institute, Chongqing 400000, P.R. China