Although epidural analgesia provides the most effective labour analgesia, it is associated with some adverse obstetric consequences, including an increased risk of instrumental delivery. Many centres discontinue epidural analgesia late in labour to improve a woman's ability to push and reduce the rate of instrumental delivery.
Torvaldsen, S., Roberts, C. L., Bell, J. C., & Raynes-Greenow, C. H. (2004). Discontinuation of epidural analgesia late in labour for reducing the adverse delivery outcomes associated with epidural analgesia. Cochrane Database of Systematic Reviews. https://doi.org/10.1002/14651858.cd004457.pub2