Uterine activity in the second stage of labour and the effect of epidural analgesia.

Uterine activity was measured during the second stage of normal labour in 20 patients with and 31 patients without epidural analgesia. There was a significantly lower uterine activity integral (UAI) in patients having epidural analgesia, and it is suggested that this may contribute to the increased rate of instrumental delivery associated with epidural analgesia.