Perineal trauma during vaginal delivery can have long-term adverse effects, including perineal pain, dyspareunia, and chronic fecal incontinence, and may increase the risk of development of recto-vaginal fistulas. Third-degree lacerations are defined as tears that extend into the perineal muscles and fibers of the rectal sphincter, while fourth-degree lacerations extend into the rectal mucosa. These are considered severe lacerations, and they occur in approximately 5 percent of vaginal deliveries. Epidural analgesia has become more popular and, in some institutions, is used in more than 70 percent of vaginal deliveries. However, few studies have examined the association between epidural analgesia and severe perineal lacerations, and currently published studies show inconsistent results. Carroll and associates assessed the question of whether epidural analgesia is an independent risk factor for severe perineal laceration during vaginal delivery.

The study was a retrospective cohort analysis of all vertex vaginal deliveries at one hospital from June 1996 through June 2000. To qualify for the study, patients had to have a spontaneous or induced vaginal delivery of a singleton, live neonate of at least 36 weeks' gestation. Patients with diabetes or severe cardiovascular disease were excluded from the analysis. The main outcome measure was the occurrence of a third- or fourth-degree perineal laceration, as defined by the American College of Obstetricians and Gynecologists. Other variables recorded included type of analgesia (i.e., epidural, local, or none), number of pregnancies and previous deliveries, use of episiotomies, the specialty of the delivering physician, and use of instrument aids (i.e., vacuum, forceps, or none).

A total of 2,759 patients qualified for the study. Epidural analgesia was given to approximately 23 percent of patients during the study period. The overall severe perineal laceration rate was 6.38 percent; 10.25 percent of women with epidural analgesia had severe perineal lacerations compared with 5.22 percent of those who did not have an epidural. Controlling for other variables, the use of epidural analgesia was a significant predictor of severe perineal injury. When instrument use was included in the analysis, epidural analgesia was no longer a significant predictor of severe perineal lacerations. Instrumentation was found to be a strong predictor of severe perineal laceration, but the use of epidural analgesia significantly predicts instrumentation use.

The authors conclude that epidural analgesia during vaginal delivery increases the risk of severe perineal lacerations secondary to a threefold increase in the risk of instrumentation use. The use of instrumentation during vaginal delivery more than tripled the risk of severe perineal lacerations in this study.