Many women will use heat packs to help them with their labour pain. Many hospitals will provide heat packs of some description, but they can also be good to have at home for prelabour and early labour, for use 'in transit' on the way to the hospital and as an option to have them at various times throughout the labour. They can also be invaluable for 'afterpains' once the baby is born.
Some hospitals ban heat packs. This is often because they are concerned that the woman's skin may be burnt. (Some women will sign a disclaimer for this.) Other hospitals dislike women using heat packs that need to be microwaved (because of fire hazards). Some hospitals supply large, heavy heat packs that are soaked in hot water urns before use and wrapped in towels. These can be effective but are quite heavy. Many woman like these for back pain during labour. Some hospitals use flasks of IV fluid (otherwise used for drips). They heat them in a their linen warmer or in buckets, or bowls, of hot water. Check with your birthplace on 'what the go' is!
NOTE: it is important to wrap heat packs and hot water bottles in towels or pillowcases to make sure you do not burn your skin. Labouring women are often not aware that their skin is being burnt, particularly in the active phase of 1st stage of labour when the contractions are strong. On rare occasions, it has been known for women to end up with skin blisters from the heat packs, realising this after the baby is born.
Care should also be taken if you have had some form of pain relief. This is something your partner or support person will need to be aware of. Don't keep using heat packs after the woman has had an epidural (she cant feel it anyway!) As the support person, look for redness of the woman's skin and feel the heat pack yourself to gauge the heat. Try removing the heat pack between each contraction. This gives her skin a break and can help add to their effectiveness when the pain starts again.