1. Department of Obstetrics and Gynecology; Linfen People's Hospital; Linfen Shanxi China
2. Department of Obstetrics and Gynecology; Ningxia Medical University; Yinchuan Ningxia China
3. State Key Laboratory of Cancer Biology; Department of Pathology; Xijing Hospital; Fourth Military Medical University; Xi'an Shaanxi China
4. Department of Gynecology; The First Affiliated Hospital of Xi'an Medical College; Xi'an Shaanxi China