Comparative Analgesic Effects of Intradermal and Subdermal Injection of Sterile Water on Active Labor Pain

BACKGROUND: The labor pain is one of the factors encouraging pregnant women for cesarean section delivery. Recently, intradermal and subdermal injection of distilled water has shown to be effective in improving this pain. OBJECTIVES: The present study aimed to determine which method has a greater impact on labor pain reduction. METHODS: In this double-blind, randomized clinical trial, 121 nulliparous women with a gestational age of ≥ 37 weeks were randomly divided into three groups: (1) 0.5 cc sterile water injection subdermally at four sacral points with insulin needles (n = 40); (2) 0.5 cc sterile water injection intradermally (n = 39); and (3) needle contact with the mentioned points as the placebo (n = 42). Before the intervention, the VAS score was measured for labor pain, and it was repeated 10, 30, 60, and 90 min after the intervention. The results were compared between the three groups. RESULTS: Before the intervention, the mean VAS pain score had no significant difference between the three groups. However, 30, 60, and 90 min after the intervention, the mean pain score was significantly lower in the intradermal and subdermal injection groups than in the control group (P = 0.001); however, the difference between the intradermal and subdermal injection groups was not significant. CONCLUSIONS: The injection of distilled water by either intradermal or subdermal method was associated with a significant reduction in the pain score during labor, but there was no difference between these two methods in terms of decreasing labor pain. As sterile water injection is a safe, effective, and low-cost method, it is proposed to increase the knowledge of midwives and obstetricians about this method.