Early Versus Late Epidural Analgesia and Risk of Instrumental Delivery in Nulliparous Women: A Systematic Review

The relationship between the timing of epidural anesthesia during labor with delivery and outcome of labor is controversial. A systematic review published in 2007 found a similar rate for cesarean delivery and instrumental vaginal delivery for early epidural analgesia and control group. These results have been questioned, however, because of the use of a broad definition of the early group (before 4–5 cm dilatation) and an incomparable control group. The primary aim of this report was to review recent literature on the effect of the timing of epidural analgesia on the rate of cesarean or instrumental vaginal deliveries in nulliparous women at a gestational age of at least 36 weeks. A search in electronic databases (Pubmed, EMBASE, and the Cochrane Library) was performed until 2010 for randomized controlled trials and prospective and retrospective cohort studies evaluating the effects of early epidural analgesia defined as cervical dilatation ≤3 cm (including combined-spinal epidural) and late-phase epidural analgesia (at least 4 cm) on the mode of delivery in nulliparous term women. The main outcome measure was the rate of cesarean deliveries or instrumental vaginal deliveries. Data extraction was completed using a data extraction form. All study data were pooled. Of the 203 individual studies identified in the initial search, 183 were excluded after review of the abstracts, leaving 20 relevant articles, 6 of which fulfilled inclusion criteria. These 6 studies included 5 randomized controlled trials and 1 retrospective cohort study, and they involved a total of 15,399 nulliparous women. There was no significant difference in the pooled risk of cesarean (risk ratio, 1.02; 95% confidence interval, 0.96–1.08) or instrumental vaginal (risk ratio, 0.96; 95% confidence interval, 0.89–1.05) deliveries among women receiving early epidural analgesia compared with those receiving late epidural analgesia. These findings show no increased risk for cesarean delivery or instrumental vaginal delivery among women receiving early epidural analgesia.