1. Department of Obstetrics and Gynecology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
2. College of Public Health and Health Management, Chongqing Medical University, Chongqing 400016, P.R. China
3. Institute of Life Sciences, Chongqing Medical University, Chongqing 400016, P.R. China