Razi Journal of Medical Sciences

Background: Labor is a painful event and its pain is one of the most severe one. Reducing this pain, for lowering the negative effects on pregnant women and also labor progress, has always been under serious concern. The purpose of the present study was to compare the effect of entonox and oxygen for lowering labor pain and also its effect on the progress of labor.

Methods: A randomized clinical trial was performed on 120 nulliparas pregnant women who had been admitted in the labor ward of Akbarabadi Teaching Hospital for termination of pregnancy, They had labor pain and were in the active phase of labor, thus enterd the study and randomly were assigned into the two groups of entonox (case group) and oxygen group (control group) (each group with 60 women). Pain was evaluated using Visual Analogue Scale (VAS). Duratin of the active phase and second stage of labor and also the total duration of labor and pain and adverse effects were compared between the two groups.

Results: The women of the two groups did not have significant differences according to age (p= 0.6), gestational age (p= 0.4), BMI (p= 0.9), neonatal weight (p- 0.6), Apgar score of 1 and 5 minutes and cesarean deliveries (p= 0.2). Mean pain score at different times (hours 1, 2, and 3) (p< 0.05) was lower in entonox group. Mean duration of labor (p= 0.003), active phase of labor (p= 0.02), and second stage of labor (p=0.02) were lower in entonox group. Side effects were more in the entonox group (p= 0.001).

Conclusions: Entonox is effective for pain relief. It also reduces the duration of labor, however, its side effects are more than oxygen.