Gas (Entonox)

One option for pain relief during labour is nitrous oxide gas mixed with oxygen. It is also called Entonox, laughing gas or just 'gas'.

You breathe in the gas through a mouthpiece or mask that's connected by a tube to a gas supply.

When you want to use gas for pain relief, you hold the mouthpiece or mask to your mouth and breathe in deeply.

Gas is usually only used during contractions. It works best if you start breathing the gas about 30 seconds before a contraction starts. You can also start breathing the gas at the start of a contraction.

When using the gas, breathe deeply, at the normal rate (not faster than usual). Stop using the gas when you feel the contraction easing.

You can stop using the gas any time you want. Hold the mask or mouthpiece yourself, so you can stop using it straight away when:

• you don't need it
• if you have side effects

Nitrous oxide gas mixed with oxygen can help:

• reduce pain intensity during your contractions
• reduce anxiety during labour and help you relax

There are many reasons you might use gas during labour:

• It helps relieve pain.
• It can be used at any stage of labour.
• It doesn't have effects on your baby.
• It doesn't stay in your body for very long.
• You can control the amount of gas you use.
• You can move and change position between contractions.
• You can use it with some other forms of pain relief.

Some disadvantages to using nitrous oxide gas mixed with oxygen are:

• It's only partly effective for some people — it might only dull the pain without decreasing it enough.
• People with some medical conditions shouldn't use it.

Nitrous oxide has no known bad effects on your baby.

Some people have side effects with gas, such as:

• dizziness
• light-headedness
• nausea (feeling sick)
• vomiting (being sick)

If you breathe in too much gas, you may become drowsy or briefly unconscious. But you will usually recover quickly once you stop breathing in the gas.

You are unlikely to use too much gas if you are holding the mouthpiece yourself. Your midwife will also check on you when using the gas to make sure you are using it safely.

You can ask your midwife, doctor or obstetrician of gas is suitable for you. They will be able to answer your questions and show you how to use the mouthpiece or mask.

Royal Women's Hospital has information on managing pain in labour. There are also some fact sheets available in different languages.