Does epidural analgesia prolong labor and increase risk of cesarean delivery? A natural experiment

OBJECTIVE: More than 50% of pregnant women in the United States are using e pidural analgesia for labor pain. However, whether epidural analgesia prolo ngs labor and increases the risk of cesarean delivery remains controversial . STUDY DESIGN: We examined this question in a community-based, tertiary mili tary medical center where the rate of continuous epidural analgesia in labo r increased from 1% to 84% in a 1-year period while other conditions remain ed unchanged-a natural experiment. We systematically selected 507 and 581 s ingleton, nulliparous, term pregnancies with spontaneous onset of labor and vertex presentation from the respective times before and after the times t hat epidural analgesia was available on request during labor. We compared d uration of labor, rate of cesarean delivery, instrumental delivery, and oxy tocin use between these two groups. RESULTS: Despite a rapid and dramatic increase in epidural analgesia during labor (from 1% to 84% in 1 year), rates of cesarean delivery overall and f or dystocia remained the same (for overall cesarean delivery: adjusted rela tive risk, 0.8; 95% confidence interval, 0.6-1.2; for dystocia: adjusted re lative risk, 1.0; 95% confidence interval, 0.7-1.6). Overall instrumental d elivery did not increase (adjusted relative risk, 1.0; 95% confidence inter val, 0.8-1.4), nor did the duration of the first stage and the active phase of labor (multivariate analysis; P > .1). However, the second stage of lab or was significantly longer by about 25 minutes (P < .001). CONCLUSION: Epidural analgesia during labor does not increase the risk of c esarean delivery, nor does it necessarily increase oxytocin use or instrume ntal delivery caused by dystocia. The duration of the active phase of labor appears unchanged, but the second stage of labor is likely prolonged.