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Obstetrics

Pain relief in childbirth 

During childbirth, the pain experienced by women as they undergo labour can lead to exhaustion and feelings of frustration, further draining the woman of vital energy that she will need later in the birthing process.

To help alleviate this, there are different groups of medicinal pain relief available to mothers during childbirth: inhaled nitrous oxide/oxygen mixture (e.g. ENTONOX), systemic opioids (e.g. pethidine) or regional analgesia (e.g. epidural). Although ENTONOX does not completely eliminate the sensation associated with contractions, it reduces the level of pain and anxiety to make them more manageable.

It can be used during early labour to help mothers cope with the pain during contractions and, if required, for uncomfortable vaginal examinations. It is generally used towards the end of the first stage of labour. The gas mixture allows, as near as possible, the mother to experience the sensation of a natural birth.

Giving mothers control over their bodies 

ENTONOX, a ready-to-use gas mixture consisting of 50% nitrous oxide and 50% oxygen is the most commonly used inhalation agent in obstetrics today. It is an effective method of pain relief for mothers who want to remain in control during labour (1, 2). ENTONOX is self-administered under the supervision of midwives, allowing mothers to adjust their intake to suit their own individual pain thresholds and comfort levels. By keeping track of their contractions, mothers can time their intake for maximum effect.

Benefits in childbirth 

The advantages of ENTONOX in pain relief have been known for many years. It is easy to use, safe and less resource-demanding than other analgesic techniques offered during labour; such as epidural analgesia (3). Compared to other methods of pain relief, ENTONOX does not prolong the duration of labour (1). It is non-invasive, has a rapid onset of action, is predictable with minimal side effects and is designed for ease of use and handling.

In a study by Holdcroft and Morgan ENTONOX was demonstrated to provide a superior analgesic effects for mothers in labour compared to pethidine (7).

Effects on mother and baby? 

ENTONOX is known to cross the placenta but has no known negative effects on the baby. In fact the oxygen component will increase the levels of oxygen in the bloodstream, which ultimately will pass via the placenta to the baby. This is good for the baby, especially during labour contractions (2).

In addition to providing effective pain relief, ENTONOX is reassuringly safe to both mother and newborn. There are also no known negative effects on breathing, circulation, the ability to push or other bodily functions (4, 5, 6). Any minor effects, such as dizziness and/or nausea, will wear off quickly after cessation of inhalation.

This method of pain relief has gained widespread acceptance in many countries due to its safety, simplicity and self-regulated delivery.

(1) Rooks JP. Nitrous oxide for pain in labor – why not in the United States? Birth 2007 March; 34(1):3-5.
(2) Rosen MA. Nitrous oxide for relief of labor pain: a systematic review. Am J Obstet Gynecol 2002 May; 186(5 Suppl Nature):S110-26. Review.
(3) Kronberg JE, Thompson DEA. Is nitrous oxide an effective analgesic for labor? A qualitative systematic review in Evidence Based Obstetric Anaesthesia, ed. by Halpern SH, Douglas MJ; Blackwell 2005, pp. 38-55.
(4) O’Sullivan I, Benger J. Nitrous oxide in emergency medicine. Emerg Med J 2003 May; 20(3):214–7. Review.
(5) Faddy SC, Garlick SR. A systematic review of the safety of analgesia with 50% nitrous oxide: can lay responders use analgesic gases in the prehospital setting? Emerg Med J 2005 Dec; 2(12):901–8.  Review.
(6) Bhattacharya S, Wang T, Knox F. Analgesia for labour pain – analysis of the trends and associations in the Grampian region of Scotland between 1986 and 2001. BMC Pregnancy Childbirth 2006 Apr 19; 6:14.
(7) Holdcroft A, Morgan M, The Journal of Obstetrics and Gynaecology 1974;81:603-607.

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