1. School of Medicine, Shandong University, Jinan, Shandong 250012, P.R. China
2. Department of Gynecology and Obstetrics, Tengzhou Central People's Hospital, Zaozhuang, Shandong 277500, P.R. China
3. Department of Gynecology and Obstetrics, The Affiliated Hospital of Binzhou Medical College, Binzhou, Shandong 264003, P.R. China
4. Department of Gynecology and Obstetrics, The Second Hospital of Shandong University, Jinan, Shandong 250032, P.R. China
5. School of Life Sciences, Shandong University, Jinan, Shandong 250100, P.R. China
6. Department of Gynecology and Obstetrics, The First People's Hospital of Jining, Jining, Shandong 272000, P.R. China
7. Department of Gynecology and Obstetrics, Qilu Hospital, Shandong University, Jinan, Shandong 250012, P.R. China