Mothers who are breastfeeding their babies will often express (or pump) milk to store it for later use. This is helpful if a mother returns to work, shares feeding responsibilities with other caregivers, or needs to be away from the baby for an extended period of time. There are a few ways to safely store breast milk, and knowing how to store your breast milk will ensure that it's ready for your baby's use.
How to Store Breast Milk Safely
Depending on when your baby will be drinking it, your breast milk can be stored in various ways:
Storing breast milk at room temperature. At room temperature (up to 77 degrees Fahrenheit), breast milk will stay safe for your baby for up to 4 hours. Ideally, your breast milk should be kept as cool as possible — experts also recommend covering the milk with a clean, cool towel to ensure safety. If your baby has eaten part of the breastmilk, the rest should be used or thrown away within 2 hours.
If stored in an insulated cooler bag surrounded by fully-frozen ice packs, breast milk will remain safe for up to 24 hours.
Storing breast milk in the refrigerator. Breast milk is safe in a refrigerator (around 40 degrees Fahrenheit) for up to 8 days, but it is best to use it within 4 days. It's best to refrigerate or chill your breast milk right after it is expressed to maximize the amount of time it will remain safe. If you add freshly-expressed milk to an already-refrigerated container of milk, cool it down before adding it.
To reheat breastmilk that has been stored in a refrigerator, place it in a small bowl and run it under warm water — not too hot. You should never microwave breast milk. Not only is it possible to scald your baby if it heats unevenly, but the process also destroys some of breast milk's beneficial compounds. Test the temperature before giving it to your baby; it should be warm on your wrist, but not hot.
Freezing breast milk. If you do not plan to use breast milk within 4 days of use, it is best to freeze it. Remember that the milk will expand as it freezes, so do not overfill the bags or containers. Be sure to mark the date that the milk was collected, and use the oldest milk before the newest. This ensures that your collection is rotated and none of the milk expires.
According to the CDC, breast milk is best frozen for up to 6 months. However, it can be safe to use up to one year (12 months) after being frozen.
When thawing breast milk that has been frozen, there are two ways to safely do so. You can place it in the refrigerator to allow it to thaw slowly over a period of around 24 hours, or you can run it under warm water. Like milk that has been stored in the refrigerator, it should never be microwaved. When warmed, swirl the milk around as some of the fats may have separated — this is completely normal and does not indicate that the milk has gone bad.
Once thawed to room temperature, use the breast milk within 4 hours or throw it away. Once heated, it should be used within 2 hours or thrown away. The CDC recommends strongly against refreezing breast milk that has previously been thawed.
Preparing to Express Breast Milk
Before pumping breastmilk, it's important to make sure your hands, any pump parts, and collection containers are clean. This is the first step to ensuring that any expressed or pumped milk is safe for your baby.
It is also important to have an appropriate storage container for breast milk. The CDC recommends using exclusively bags or bottles designed for storing breast milk to avoid contaminants like BPA. Do not use disposable plastic bags or plastic bottle liners for storing breast milk. The best options are sealable breast milk storage bags or glass containers with tight-fitting lids.
After expressing milk, clearly label the container with your name and the date that it was collected. It is also best to store breast milk in small batches from 2 to 4 ounces, especially for newborn babies, since it is not safe to reheat it multiple times.