1. Department of Gynaecology, Weifang Yidu Central Hospital, Weifang, Shandong 262500, P.R. China
2. Department of Gynaecology and Obstetrics, Weifang Brain Hospital in Shandong, Weifang, Shandong 261000, P.R. China
3. Department of Medical Record Information Section, The Chinese People's Liberation Army 89 Hospital, Weifang, Shandong 261021, P.R. China
4. Department of Gynecology, Weifang People's Hospital, Weifang, Shandong 261041, P.R. China