An Investigation into the Side Effects of Entonox on Primiparas in Painless Labor

Labor pain causes a great fear of vaginal delivery as well as increase of cesarean among women. Therefore, using harmless and efficacious pain relief methods is of great significance. Accordingly, the present study aimed at investigating the side effects of nitrous oxide on mother and fetus. This is a randomized controlled trial study carried out on 178 primipara candidates for natural. During the active labor phase, women were assigned to two groups; intervention group(89 women inhaling Entonox) and control group(89 women inhaling oxygen). The required data including age, gestational age, evidence of abruption, mode of delivery, meconium staining, fetal Apgar score, side effects of drug consumption, the amount of postpartum bleeding, initial hemoglobin concentration and its concentration 6 hours after delivery were recorded. Then the data were analyzed using SPSS software v.16, Chi-square formulas. There was no significant difference between the two groups in terms of the evidence of abruption, accelerated labor, meconium staining by the fetus, mean Apgar scores at 1 and 5 min and the final mode of delivery(P>0.05). Side effects such as dizziness and dry mouth were reported in the group inhaling Entonox. In two modes of vaginal delivery and cesarean section, the mean reduction in hemoglobin concentration 6 hours postpartum in the group inhaling Entonox was less than that in the control group(P<0.05). Compared to the use of oxygen, the use of Entonox gas for painless labor did not cause adverse effects on the mother and fetus; however, only minor side effects including drowsiness and dry mouth were observed. Furthermore, it was observed that Entonox causes less reduction in hemoglobin concentration of mother which may pertain to its positive effects on labor progress and its duration.