Whether you are bottle feeding with expressed milk or formula milk, most babies will prefer to have their milk slightly warmed (especially if it has been prepared earlier and then stored in the fridge to be kept sterile). If you are new to bottle feeding, don't forget to check out preparing feeding bottles to get the basics right.
How warm should a bottle feed be?
Babies do tend to vary a little on what they like. Some babies are happy to drink fairly cold milk, but most will be used to breastmilk which comes warm direct from their mother and therefore making the milk slightly warm is a good idea.
Some babies will just want the edge taken off cold milk and have it quite tepid (especially in warmer weather), while other babies will turn their away unless the milk is warmer.
Never make the milk too hot as it was easily scald your baby's tongue and mouth. It should feel just warm, not as hot as your own hot drinks would be.
To test the temperature of the milk, drop a little onto the soft side of your wrist (that is, hold your hand palm side up and then drop some milk onto your wrist) as this part of your hand will be more sensitive to how hot or cold the drink is. If it is too hot, either leave it to cool for a few minutes (keep the lid on because, even if this means cooling takes longer, the teat will be kept sterile) or put it in a bowl or jug of cold water to cool it down.
Safe milk warming
Although many parents like to warm milk bottles in the microwave this is a very dangerous practice. The heating process of microwaving does not heat evenly and can create 'hotspots' in the drink after the bottle has been removed and given to your baby. Some parents shake the feed well after microwaving in order to even out the hot milk, but this can make the feed more bubbly and give your child hiccups. Microwaving milk feeds is not best practice.
Warming a milk feed is quick and easy to do. Some companies like Avent sell bottle warmers which you can set to the right bottle size and leave to warm your feed. However, they do not switch themselves off so if you forget about a feed, you will find that the milk gets very hot. That said, if you are busy, just plonking the milk in the warmer rather than boiling a kettle etc might be more convenient.
Otherwise, boil a kettle of water and then stand the bottle in a pan or heat-proof jug for a few minutes. This is a good method as it rarely overheats the milk before the water itself starts to cool down.
Some formula milks can turn bitter to taste if they are overheated, even if you then cool the milk down again before giving it to your child. If your baby rejects a feed with a milk he is used to, think about whether overheating might be the cause.
If you heat milk and then do not feed it straight away, start again with another feed later rather than reheating the one you have already prepared.