The relationship between epidural analgesia and cesarean delivery remains controversial. Several studies have documented an association, although others have not. This inconsistency may result from an association between severe labor pain and dystocia. We hypothesized that dystocia causes severe labor pain, such that more epidural medication is required to maintain comfort. We examined the relationship between labor outcome and severe pain, defined by the number of supplemental epidural boluses. We retrospectively reviewed the anesthesia records of 4493 parturients who received small-dose labor epidural analgesia. An independent association was found between operative delivery and maternal age, body mass index, nulliparity, fetal weight, induction of labor, and the number of boluses required during labor. By using multivariate analysis, the odds ratio of cesarean delivery among women who required at least three boluses was 2.3 compared with those who required two boluses or less. No association was found between the concentration of bupivacaine in the epidural infusion and operative delivery. Because women with cesarean deliveries appeared to have more pain, degree of labor pain may be a confounding factor in studies examining epidural analgesia and outcome.

Implications:

This is a retrospective observational study demonstrating an association between labor pain and cesarean delivery. Our results provide an alternative explanation of why epidural analgesia is associated with cesarean delivery.