Recent research has suggested that 6 cm of cervical dilation should be the threshold for the active labor phase, and it has confirmed that epidural analgesia (EA) is a safe method of pain relief during labor. However, the evidence provided for these findings comes mainly from randomized controlled clinical trials (RCTs), which suffer from the limitation of real-world generalizability. To test the generalizability of the conclusions from these previous RCTs, we conducted a prospective cohort, real-world study (RWS) on 400 Chinese term nulliparas. A total of 200 of the participants (the EA group) received EA upon request. The participants in the EA group were further subdivided as follows according to their cervical dilation when the EA administration was initiated (CDE): [EA1 group (CDE < 3 cm), EA2 group (3 cm <= CDE < 6 cm), and EA3 group (CDE >= 6 cm)]. We compared the labor duration of the EA group versus the non-EA (NEA) group, and the NEA group versus the 3 EA subgroups. We also compared delivery outcomes between the EA and NEA groups. The median total labor duration for the EA group [676 (511-923) minutes] was significantly longer than that of the NEA group [514 (373-721) minutes] (P < 0.001). The median durations of both the first- and second-stages of labor for the EA group [600 (405-855) minutes, 68 (49-97) minutes] were longer than those of the NEA group [420 (300-630) minutes, 50 (32-85) minutes] (P < .001, P < .001)]. In addition, the median total labor durations in both the EA1 [720 (548-958) minutes] and EA2 groups [688 (534-926) minutes] were longer than in the NEA group (P P < .001, respectively), and the first- and second-stage labor durations of these subgroups were similar to their total labor durations. A Cox regression analysis showed that EA was associated with longer first-stage labor [hazard ratio (HR) 0.55, 95% confidence interval (CI) 0.42-0.71, P < .001] and longer second-stage labor (HR 0.66, 95% CI 0.51-0.85, P = .001). The delivery modes and neonatal outcomes between the EA and NEA groups were not statistically different, however. Our findings suggest that EA administered before a cervical dilation of 6 cm may be associated with longer total, first-, and second-stage labor durations compared with no EA, while later EA administration is not. In addition, though EA prolongs labor duration, it does not impact delivery outcomes. These results confirm the significance of a 6 cm cervical dilation threshold in real-world labor settings.