1. Department of Obstetrics and Gynecology, West China Second University Hospital, Sichuan University, Sichuan 610000, P.R. China
2. Department of Infectious Diseases, People's Hospital of Deyang City, Deyang, Sichuan 618000, P.R. China
3. Department of Pathology, People's Hospital of Deyang City, Deyang, Sichuan 618000, P.R. China