My wife need to go to hospital for some hours, maybe day. She can pump out some milk from her breasts but we have no idea how to store it properly, how long we can store it and if we need to do something before I can fed our newborn (I guess that I need to warm bottle to proper temperature). Are there any tips how to handle this situation?
Breast milk can keep up to six months in the freezer, up to 3-4 days in the fridge, and up to 4-6 hours outside it (a lactation specialist once told me). So the best solution in your case is to put it in the fridge. Put it into a sterile container such as a sterilized bottle. You can also divide it into portions depending on how much your baby drinks normally, and how much there is.
Before giving it to your child, warm it (not too much!) and be sure to shake the bottle a bit because the fat will separate from the water. Or maybe shake first and then warm.
We always froze it, then if you forget about it/don't need it/whatever, you're fine.
Once frozen, it can keep for 6 months, some sources say more.
To use it, sterilize a bottle, warm the frozen milk in a bath of warm water, then pour into the bottle. Do not microwave at any step.
Maybe I'm maybe taking for granted here the storage mechanism: