OBJECTIVETo estimate the effect of epidural analgesia on the Friedman labor curve.METHODSThis study was a secondary analysis of a previously reported randomized trial of the effects of patient-controlled epidural analgesia during labor compared with patient-controlled meperidine on cesarean delivery rate. All subjects had a singleton, cephalic, nonanomalous fetus at or beyond 37 weeks' gestation. This secondary analysis was limited to women who had cervical dilatation commencing of at least 3 cm (ie, active phase of labor).RESULTSA total of 459 women were randomized. Twenty-five women were excluded for a cervix less than 3 cm dilated, leaving 220 women allocated to patient-controlled epidural analgesia and 214 to patient-controlled intravenous meperidine available for analysis. There were no significant demographic differences between the two groups, including age, race, gestational age, and cervix on admission. The active phase of labor was 1 hour longer in the epidural-treated group (6.0 ± 3.2 hours versus 5.0 ± 3.2 hours,P< .001). The rate of cervical dilation was significantly less with epidural analgesia (1.4 cm/h versus 1.6 cm/h,P< .002). The duration of the second stage tended to be longer in the epidural group (1.1 ± 1.5 hours versus 0.9 ± 1.0 hours,P= .079).CONCLUSIONEpidural analgesia prolonged the active phase of labor by 1 hour compared with Friedman's original criteria.