Background : Pain relieving is one of the main aspects of obstetrics. Mental and physiologic complications of acute labor pains on fetus and mother are well known. In our maternity hospitals, relieving the labor pain is not routinely applied. Hence, it seems necessary to evaluate the cheap and safe methods in this regard. The present study has been accomplished in 2001 on those referring to Tehran ’s Mahdieh maternity hospital, with the aim of comparing the impact of inhalation of a mixture of oxygen and nitrous oxide (Entonox) with Transcutaneous Electrical Nerve Stimulation (TENS) on the labor pain.

Materials and methods : 60 volunteer parturients were randomly placed in two groups of TENS and Entonox. The two groups were the matched according to the labor stimulation and the number of parities. The relevant data were collected via the questionnaire, observing and physical examination. Mothers of both groups applied each method in the form of self administering and showed their pain severity in certain intervals (4-5 cm, 6-7 cm, 8-9 cm, 10cm dilatations) to the researcher using visual analog scale.

Results : The mean of the pain severity in the whole active phase of labor was 6.91±1.03 in the TENS group and 5.18±1.15 in Entonox. (p=0.0001).

Conclusion : Results have revealed that application of Entonox relieves the pain of the active phase of labor more satisfactory than TENS. The two mentioned ways left no negative or harmful impressions on the fetus and mother. Further studies in order to compare Entonox with other pain relieving techniques are recommended.