1. Department of Obstetrics and Gynecology, The First Affiliated Hospital of the University of Science and Technology of China, Anhui Provincial Hospital, Hefei, Anhui 230001, P.R. China
2. Department of Gynecology and Obstetrics, The Second Affiliated Hospital of Anhui Medical University, Hefei, Anhui 230601, P.R. China
3. Department of Gynecology and Obstetrics, Qilu Hospital of Shandong University, Jinan, Shandong 250012, P.R. China