I'm not breastfeeding currently, but hope to be getting pregnant again in the near future. My question is about storing breastmilk and reheating it when it's needed. How do I do that? I've looked for the answer before, but never found anything very straightforward.
My Medela breastpump came with a little fridge magnet that reminds you how long breastmilk can be kept in certain locations (room temp., fridge, freezer in fridge, separate freezer, etc.). It's really handy.
If I expect to use the milk within a few days, I'll just keep it in a bottle or something in the fridge. If it's more than one serving's worth, I'll pour one serving's worth into a separate bottle. If she's drunk from a bottle but I expect her to have some more within a few hours, I'll just put the milk back into the fridge to reuse, although you're not supposed to do that.
For milk that I want to save for a while, I freeze it. You can freeze it in bottles or in little breastmilk freezer bags. Some breastpumps let you pump directly into the bags; mine you have to pump into bottles, then pour the milk into the bag. If you seal the bag well, you can lay the bag on its side to freeze so that it sort of becomes a fairly flat rectangle. That makes them easy to stack so you can store a lot of milk. I write on the bag with a Sharpie what the date frozen is, so I can make sure to use the oldest ones first. Yes, you can freeze milk for a long time. But milk also changes over time as your baby grows, so ideally you don't want to give milk pumped for a 2-month-old baby to a 9-month-old baby, even if it's technically still good. The balance of sugars and fats, I think, is different.
To thaw the milk, you can put it in the fridge overnight if you have time. If you need it thawed immediately, you can heat some water, then put the frozen bag/bottle into the hot water to thaw. I do the same thing, although obviously for less time, to heat the milk up. You'll want to shake it around a bit, obviously, to get it evenly mixed and avoid hot spots. You're never supposed to heat it directly in the microwave.