Subcutaneous vs intravenous fentanyl for labor pain management: a multicenter randomized controlled trial

Background: Labor pain is the most intense pain a woman will experience during her lifetime. Epidural anesthesia is recommended as the most effective method for pain relief, but it has several limitations. Fentanyl has high analgesic potency with short-acting duration, but the large-scale trials that assessed the effectiveness and safety of it for labor pain management are still limited.

Objective: This study aimed to compare the effectiveness and harm and maternal satisfaction of subcutaneous vs intravenous fentanyl for labor pain management.

Study design: We conducted a multicenter, open-label randomized controlled trial. A total of 226 women were randomized to receive intravenous or subcutaneous fentanyl for labor pain management. Pain scores were evaluated before and after fentanyl administration at 5, 30, and 60 minutes and then every 60 minutes until delivery. The data were analyzed based on the intention-to-treat principle.

Results: Both intravenous and subcutaneous fentanyl significantly decreased labor pain from baseline to delivery (overall mean change, -1.39; 95% confidence interval, -1.62 to -1.17; and -0.89; 95% confidence interval, -1.24 to -0.05, respectively). The reduction in the pain score between the 2 groups was not different (overall mean difference, -0.35; 95% confidence interval, -0.76 to 0.05). Maternal satisfaction was high for both intravenous and subcutaneous fentanyl (89.4% and 93.8%, respectively). There was no difference in the maternal satisfaction rate between the 2 groups (relative risk, 0.95; 95% confidence interval, 0.88-1.03). No serious maternal and neonatal adverse effects were observed.

Conclusion: Both intravenously and subcutaneously administered fentanyl were safe and significantly reduced pain from baseline to delivery among low-risk pregnancies. Maternal satisfaction with the childbirth experience was high regardless of the route of administration of fentanyl. No serious adverse effects of fentanyl were observed in either the mothers or the neonates.