Objective: To compare the efficacy between meperidine and fentanyl for labor pain reduction.

Materials and Methods: The present study was a randomized controlled trial conducted in term singleton pregnant women planning for vaginal delivery, between August 7, 2017 and January 6, 2018. Women with opioid allergy, addictive substance abuse in the last year, asthma, fetus with anomalies, or cervical dilation more than 8 cm were excluded. The participants were allocated to receive either intravenous meperidine (50 mg every two hours) or fentanyl (50 mcg every hour) during active phase of labor as maternal requested. Pain score was assessed at 0, 30, 60, and 120 minutes by a 10-point numeric rating scale.

Maternal and fetal adverse effects, number of opioid administrations, route of delivery, and neonatal outcomes were evaluated.

Results: Ninety-two subjects were allocated to meperidine (n = 46) and fentanyl (n = 46). Pain score at 30 minutes was reduced in both groups (meperidine 0.85±1.38 versus fentanyl 0.89±1.69, p=0.893), and pain scores were similar at 30, 60, and 120 minutes (p=0.779). Women in the fentanyl group experienced less nausea and drowsiness, and a more rapid heart rate but without significant difference. Abnormal fetal heart rate pattern after sedation occurred with similar frequency in both groups (meperidine 19.6% versus fentanyl 17.4%, p=0.788). No newborns required naloxone treatment.

Conclusion: Fentanyl is as effective as meperidine to relieve labor pain with comparable maternal, fetal and neonatal adverse effects.