1. Department of Obstetrics and Gynecology, The First Affiliated Hospital of Dalian Medical University, Dalian, P.R. of China;
2. Department of Obstetrics and Gynecology, The Affiliated Zhongshan Hospital of Dalian University, Dalian, P.R. of China;
3. Department of Pathology, The First Affiliated Hospital of Dalian Medical University, Dalian, P.R. of China