To gain maximum benefit you need to start breathing it as soon as you feel a contraction start. This means the maximum action is being achieved at the height of the contraction. Entonox can be used throughout both early labour and the delivery of your baby. Entonox crosses the placenta but is not known to have any effect on your baby. The higher concentration of oxygen may help your baby.
Some mothers feel light-headed during use.
Occasionally nausea can be experienced, as can tiredness. Some mothers complain of a dry mouth, so you may wish to have a glass of water to sip, or small ice cubes to suck. You may experience a tingling in your fingers. This is due to overbreathing. Entonox only works when you breath it in, so it's effects wear off very quickly once you stop breathing it, normally within a minute.