1. Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
2. Department of Obstetrics and Gynecology, Affiliated Haian People's Hospital of Nantong University, Nantong, Jiangsu 226600, P.R. China
3. Department of Obstetrics and Gynecology, Affiliated Maternal and Child Health Care Hospital of Nantong University, Nantong, Jiangsu 226018, P.R. China
4. Department of Pathology, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu 210002, P.R. China