1. The Second Clinical Medical College, Shaanxi University of Traditional Chinese Medicine, Xianyang, Shaanxi 712046, P.R. China
2. Department of Gynecology and Obstetrics, The Second Affiliated Hospital of Xi'an Medical University, Xi'an, Shaanxi 710038, P.R. China
3. Clinical Laboratory, People's Hospital of Tongchuan, Tongchuan, Shaanxi 727031, P.R. China