5Rawal N , Holmstrtm B, Crowhurst JA, et al. The combined spinal - epidural technique [J] . Anesthesia Clin North Am, 2001, 18 (2): 267-295.
6Torvaldsen S, Roberts CL No increased risk of caesarean or instrumental delivery for nulliparous women who have epidural analgesia early in ( term ) labour [J ] . Evid Based Med,2012, 17 (1): 21-22.
7Sia AT, Chong JL. Epidural 0. 2% ropivacaine for labour anal- gesia: parturient- controlled or continuous infusion [ J] . An- aesth Intensive Care, 1999, 27 (2) : 154 - 158.
8Wassen MM, Zuilen J, Roumen FJ, et al. Early versus late epidural analgesia and risk of instrumental delivery in nullipa- rous women: a systematic review [J] . BJOG, 2011, 118 (6) : 655 -661.
9Salvesen KA, Morkved S. Randomised controlled trial of pel- vic floor muscle training during pregnancy [ J J . BMJ, 2004, 329 (7462): 378-380.
10Macarthur A J, Macarthur C. Incidence, severity, and deter- minants of perineal pain after vaginal delivery: a prospective cohort study [J] . Am J Obstet Gynecol, 2004, 191 (4) : 1199 - 1204.