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.

It can take a few contractions to get the hang of knowing when to use the gas.

Gas doesn’t work for everyone. It is ok to stop using the gas any time you want and to try something else for pain relief.

Only you should hold the mask or mouthpiece, so that you can stop using it straight away when:

• you don’t need it
• you feel you’ve had enough
• you feel any side effects
• you feel drowsy (sleepy)

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 along with some other forms of pain relief.

Gas is only partly effective for some people and might only dull the pain without decreasing it enough.

People with certain medical conditions cannot use gas. Such as people who:

• have vitamin B12 deficiency (Opens in new tab)
• had recent ear surgery
• have a medical condition causing trapped air in the body, such as pneumothorax (Opens in new tab) or blocked middle ears
• have trouble maintaining oxygen levels due to a chest infection or lung disease

You also need to be able to hold the mouthpiece or facemask to get the gas. This can become difficult as the labour progresses and you get more tired.

Nitrous oxide has no known harmful effects on your baby. The gas quickly clears out from your body after a few minutes. It doesn’t affect breastfeeding, so skin-to-skin contact and feeding your baby can happen straight away.

There is also no evidence to suggest that using nitrous oxide gas as pain relief during labour causes autism.

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 if gas is suitable for you. They will be able to answer your questions and show you how to use the mouthpiece or mask.

The Royal Women’s Hospital (Opens in new tab) has information on managing pain in labour (Opens in new tab). There are also some fact sheets available in different languages (Opens in new tab).