Fig. 1. Incidence of fever among patients laboring less than 6 h, less than 12 h, less than 18 h, and all patients. The number of patients in each group is shown immediately below the corresponding bar. P values are shown for comparisons between epidural alone versus epidural + systemic nalbuphine (both), and for patients receiving epidural (with or without opioid) versus patients not receiving epidural. Differences between no analgesia and nalbuphine alone were never significant (P > 0.2 for all comparisons). Twenty patients, whose length of labor could not be determined, are excluded from the figure and calculations.