Epidural anesthesia using low concentrations of bupivacaine doesn't seem to increase the risk of Cesarean delivery, but may increase the likelihood of an instrumental vaginal delivery in nulliparous women, according to a recent meta-analysis.
The authors of the review, which included data from seven randomized, controlled trials, reported the risk of an instrumental vaginal delivery in women receiving epidural anesthesia to be about twice that of women not receiving an epidural. Women receiving the regional anesthesia also had longer second-stage labor, although their newborns seemed unharmed by it.
On a more positive note, epidurals seem to successfully do what they are supposed to do: provide adequate pain relief. Fewer of the women receiving epidurals changed to parenteral opioids than vice versa. And the neonates of women receiving epidurals were less likely to need naloxone than the neonates of women who received opioid analgesia.
Liu EHC, Sia ATH. Rates of caesarean section and instrumental vaginal delivery in nulliparous women after low concentration epidural infusions or opioid analgesia: Systematic review. BMJ. 2004;328:1410-1412.