The good news is that breastmilk can be stored safely for months (and that there is not bad news). You just have to know how to store the milk safely. Especially since many mothers are breastmilk goddesses with abundant production, exceeding what their babies can drink. And so many others are returning to work while they are still breastfeeding (and federal law requires employers to provide adequate facilities so mothers can pump and store the natural resource they produce).
Once pumped while at work, the milk can be placed temporarily in an insulated cooler with ice packs. Then the milk can be transferred to the refrigerator or freezer, and left there for days or months (as you can see from the table). To make sure you stay within bounds, it's important to label the bag or bottle.
There is a debate, which is better. Most experts prefer plastic bags, since they are concerned that the immune-active cells in breastmilk will layer against glass bottles and be lost. But recently, some breast milk banks have returned to bottle storage. Either way, remember to swirl the milk so that the fat mixes in with the rest and leave enough room in case the milk expands when it freezes.
Storage Guidelines for Breast Milk
Location Temperature Duration Comments
Countertop Room temperature 6–8 hours Must be covered
Insulated cooler 5–39°F or –15–4°C 24 hours Keep with ice packs
Refrigerator 39°F or 4°C 5 days Keep at the back of fridge;
Freezer compartment of refrigerator
5°F or –15°C 2 weeks Store at back of freezer
Freezer compartment of refrigerator with separate doors
0°F or –18°C 3–6 months
Deep freezer –4°F or –20°C 6–12 months
Source: Bailey Koch, RD, CSP
It's also important to know how to thaw and warm breastmilk to room temperature. Microwaves can create hotspots with the milk, so MICROWAVES SHOULD NOT BE USED. Instead, breastmilk should be thawed overnight if possible and then the container should be placed in a warm water bath until the milk returns to room temperature, so the baby can drink it safely.
Once the breast milk is thawed, it can be saved for up to 24 hours in the refrigerator. It should not be refrozen. So to limit any waste, breastmilk goddesses might want to store the milk in 2 -4 oz portions.