1. School of Basic Medical Science, Inner Mongolia Medical University, Hohhot, Inner Mongolia 010010, P.R. China
2. Obstetrics and Gynecology Department, The Affiliated Hospital of Inner Mongolia Medical University, Hohhot, Inner Mongolia 010010, P.R. China
3. Department of Cervical Surgery, The Second Affiliated Hospital of Inner Mongolia Medical University, Hohhot, Inner Mongolia 010010, P.R. China
4. Animal Science College, Inner Mongolia University for the Nationalities, Tongliao, Inner Mongolia 028000, P.R. China