Gas and air (Entonox) in labour

What is Entonox?

Entonox is a clear, odourless gas, commonly used for medical pain relief. It is made of equal parts of nitrous oxide and oxygen (LabourPains, no date a).

How and where is Entonox used in maternity?

Entonox can be used wherever the birth is planned. If planning a home birth, the midwife will bring Entonox with them.

Entonox is simple to use and the woman or birthing person is in control (NHS, 2023).

During labour, the pregnant woman or person inhales Entonox by breathing in through a mouthpiece or mask. The best effect is achieved when Entonox is used from the start of a contraction. It takes 15-20 seconds to work, so this gives the most benefit when the pain is strongest (LabourPains, no date a; NHS, 2023).

The woman or birthing person returns to breathing normal air between contractions (LabourPains, no date a).

After birth, Entonox may be used as pain relief during repair of the perineum (Knuf & Maani, 2023). The perineum is the area between the vagina and anus that might stretch and tear during birth. If this happens, it may need to be stitched up by a doctor or midwife.

How effective is Entonox, and how long does it last?

Entonox is an effective way of reducing pain in labour (Jones et al, 2012). It can help the woman or birthing person feel more relaxed, but it does not remove the pain completely (LabourPains, no date a).

It works quickly and is used at any time during established labour (LabourPains, no date a).

Entonox can be stopped at any time, and the effects will wear off in minutes (LabourPains, no date a).

Are there any side effects of using Entonox?

Common side effects include (Jones et al, 2012; NHS, 2023; LabourPains, no date a):

• feeling sick
• feeling light-headed or dizzy
• feeling sleepy
• a dry mouth

These effects are normally mild and go away quickly when the woman or birthing person stops using it. Taking a break between contractions reduces the effects (LabourPains, no date a).

There are no long-term effects of using Entonox for the person using it (LabourPains, no date a).

Does Entonox affect labour, the baby, or breastfeeding?

It has no impact on how labour progresses. Some people find that focusing on the breathing is calming and helpful.

While Entonox does cross the placenta, the baby or babies quickly get rid of it when they start breathing. There is no suggestion of any long-term impact on either the baby or breastfeeding (Knuf and Maani, 2023; LabourPains, no date a).

Can a birth partner help with Entonox?

The birth partner should not hold the mouthpiece in the woman or birthing person’s mouth. However, they can hold the mouthpiece between contractions, while it’s not being used. Then they can offer it back to the mother or birthing person.

This might be important when labouring in water or a birth pool, so the mouthpiece doesn’t slip into the water.

A birth partner could also offer sips of water to drink if the woman or birthing person has a dry mouth from using Entonox.

Can Entonox be used with other types of pain relief?

Entonox can be used:

• alongside a TENS machine
• while labouring in water
• before an epidural

On its own, Entonox has only mild effects on the mother or birthing person. However, it is not recommended to combine with opioid pain management. This is because the combination could have negative effects on breathing, blood oxygen levels, and sleepiness (Knuf and Maani, 2023).

Is Entonox bad for users or the environment?

While Entonox exposure during labour is not a problem, for healthcare workers who are exposed long term it can lead to problems (LabourPains, no date a).

Occasionally this means that maternity units temporarily withdraw Entonox so they can make the environment safe for staff. Alternatives will be provided for women and birthing people (LabourPains, no date a).

Entonox is a greenhouse gas and contributes to the climate warming. Using it for four hours during labour is the equivalent of driving 870 miles in a car. Maternity units are moving towards using technology to capture the gas or break it down into harmless elements (Labour Pains, no date a).

The environmental impact can be lowered by (LabourPains, no date b):

• Only using it during a contraction
• Using Entonox with a capture device when breathing out, available in some maternity units