15/12/2009 12:09 GMT | Updated 22/05/2015 06:12 BST

G: What Is Gas And Air?

Gas and air is a mix of 50 per cent oxygen and 50 per cent nitrous oxide (laughing gas). It is commonly used during labour for pain relief, especially towards the end of the first stage.

It is an odourless and colourless gas. The nitrous oxide acts as the analgesic, the oxygen prevents the mother becoming hypoxic.

Gas and air can be self-administered, using a mouthpiece or a mask. The mother simply breathes deeply but normally. An anaesthetist is not required to be present.

The effect is to take the edge off the pain rather than completely remove it. The mother will probably feel light headed and perhaps a little confused, dizzy, or sick. It can cause a dry mouth if used for a long time.

Some women find that gas and air does not offer enough relief from the pain of labour. It can be used in combination with other forms of pain relief, such as pethidine, and it can be used in a birth pool.

Gas and air starts to work very quickly (about half a minute after being inhaled). The mother should therefore start to breathe the gas and air as soon as a contraction starts so that by the time it is peaking, the pain relief should be working.

The effects wear off very quickly also. Almost immediately after the mother stops using the gas and air it will be gone from her system completely. This means there are no lasting side effects on the mother or the baby.

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