1. Department of Gynaecology and Obstetrics, The Affiliated Wuxi Maternity and Child Health Care Hospital of Nanjing Medical University, Wuxi, Jiangsu 214400, P.R. China
2. Department of Reproductive Health, Maternal and Child Health Care Hospital of Yixing, Wuxi, Jiangsu 214200, P.R. China
3. Reproductive Medicine Center, Maternal and Child Health Care Hospital of Wuxi, Wuxi, Jiangsu 214002, P.R. China