Association of epidural analgesia with cesarean delivery in nulliparas.

OBJECTIVE: To evaluate whether epidural analgesia during the first stage of labor is associated with an increased risk of cesarean delivery.

METHODS: The association of epidural analgesia and cesarean delivery was examined in a retrospective study of 1733 low-risk, term nulliparas with singleton infants in vertex presentations, in which labor began spontaneously. To evaluate the effect of epidural analgesia on cesarean deliveries, independent of other factors influencing the use of epidural analgesia, we used propensity scores to create five subgroups (quintiles) of women who, based on characteristics discernible at admission, appeared equally likely to receive epidural analgesia. Multivariate logistic regression analysis was used to control for confounding.

RESULTS: Overall, the cesarean rate among women receiving epidural analgesia was 17% (168 of 991), compared with 4% (30 of 742) among those who did not receive epidural analgesia. An increased cesarean rate among women receiving epidural analgesia was present in all propensity quintiles. In an adjusted logistic regression analysis, women receiving epidural analgesia were 3.7 times more likely to undergo a cesarean (95% confidence interval 2.4, 5.7). The greatest increase in cesarean risk was noted when epidural analgesia was administered earlier in labor, but there was a more than twofold increase regardless of the dilation and station at administration of epidural analgesia.

CONCLUSIONS: Epidural analgesia may increase substantially the risk of cesarean delivery. Although the causal nature of this association remains open to debate, prenatal care providers should routinely discuss the risks and benefits of epidural analgesia with women during their pregnancies so that they can make informed decisions about the use of pain relief during labor.