The chances are, you'll be puffing away at a tank of Entonox during labour to help relieve the pain. Here’s what you need to know about Entonox - otherwise known as gas and air...
What is Entonox?
Entonox is the brand name of a colourless, odourless gas(Knuf, 2020) usually made up of half nitrous oxide and half oxygen (NICE, 2007). This is what you'll have if you are given 'gas and air' while in labour.
Why is Entonox used in labour?
Nearly 80% of women use Entonox in labour because many find it to be the best option from a range of inhaled pain killers (CQC, 2019). Entonox has no negative effect on contractions, and you and your baby quickly get rid of it from your bodies (Jones et al, 2012).
How is Entonox used in labour?
It’s self-administered so you breathe in Entonox through a mouthpiece or mask that you grab when you need it.
You control the amount of Entonox you use, but to get the best effect it is important to get the timing right. You should start breathing Entonox as soon as you feel a contraction coming on, then it will help most when the pain is at its worst. You shouldn't use it between contractions or for long periods as this can make you feel dizzy and tingly (OAA, 2019). It takes 15 to 20 seconds to work effectively (NHS, 2017).
It is simple and quick to act and wears off in minutes (OAA, 2019).
The pain-relieving effect is caused through the release of the body's own opioids, so it has a similar effect to morphine (Knuf, 2020).
How effective is Entonox?
Entonox is said to be of ‘moderate’ help with pain and is, surprisingly, more effective at easing pain than opioids (Jones et al, 2012; OAA, 2016; OAA, 2019).
Can everyone use Entonox?
Some women say Entonox makes them feel sick so they might want to avoid it.
Nitrous oxide can cause dreaming and hallucinations and should be avoided in patients with severe psychiatric disorders (Knuf, 2020).
Using Entonox for over 24 hours can deplete the body's stores of vitamin B12, so these levels might be checked if you are at risk of a vitamin B12 deficiency.
What are women’s experiences of Entonox?
Women who use it like being able to control it themselves, (NHS, 2017) although it can make some women feel nauseous and light headed (NICE, 2007).
Does Entonox have any side effects?
There are no significant side effects for women or babies when used appropriately – in other words, during contractions only (NHS, 2017; Jones et al, 2012). Slight side effects some women experience are feeling dizzy or being sick and they often say they have a dry mouth (Jones et al, 2012; OAA, 2016; Lowth, 2017; NHS, 2017).
It does not harm your baby and it gives you extra oxygen, which may be good for you and your baby (OAA, 2019).
Does Entonox affect labour or breastfeeding?
It has no impact on how labour progresses, and there is no suggestion of any impact on breastfeeding (OAA, 2016).
Does Entonox have any long-term effects?
None on the person using it. There are concerns about its affect on midwives, who have greater exposure (Robertson, 2006), and on the environment (Campbell & Pierce, 2015).
How long do the effects of Entonox last?
You can stop taking it at any point if you choose. The effects of Entonox wear off in minutes (OAA, 2019).
Where and when can I use Entonox during labour?
You can have Entonox wherever you plan to give birth. If you’re planning a home birth, the midwife will bring Entonox with them. You can use it at any time in labour (OAA, 2019).
Can my partner help with Entonox?
Your partner can help by holding the mouthpiece between contractions, while you’re not using it, and then offering it back to you. This is particularly important if you’re in a bath or birth pool as you don’t want the mouthpiece to slip into the water.
Can I use Entonox with other types of pain relief?
Will I need any extra procedures with Entonox?
There is no need for extra monitoring or any other additional procedures with Entonox (OAA, 2016).
Are there any other considerations with Entonox?
When discussing options for working with the pain of labour, your midwife might mention the environmental impact of Entonox. This is not to discourage you from using it but because some women might make an informed decision not to. Entonox is a greenhouse gas that accounts for over 2% of the NHS carbon footprint, and about a third of that is used by women in labour (Sulbaek et al, 2012; Sustainable Development Unit, 2013).
Other pain relief options also have environmental impacts but Entonox is the first one that has been highlighted (Sustainable Development Unit, 2013). NHS Trusts will also be working to address the hospital’s environmental impact in other ways, such as lower temperatures, improved recycling, and transport (Sustainable Development Unit, 2013).
This page was last reviewed in March 2021.
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Research from the Royal College of Obstetricians and Gynaecologists (RCOG) about the use of water as pain relief in labour.
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