The inventions of the breast pump and freezer were kind to busy mothers. Freezing expressed breast milk means you'll have a supply available for your growing little one whenever he needs it -- but, even in the freezer, breast milk doesn't last forever. Once thawed, the window for safe use is small.
Breast Milk Storage Time Limits
Expressed breast milk can be kept at room temperature for up to 6 hours and still be safe for consumption, reports Mayo Clinic. By contrast, milk may be stored in a standard freezer for up to 6 months -- or as long as 12 months, in a chest freezer or other freezer that's not opened frequently. Once it's fully thawed, milk should be used within 24 hours. After that, it must be thrown away. According to Ask Dr. Sears, milk that has been frozen is more prone to bacterial growth than fresh milk.
Freezing Breast Milk
Build up a supply of frozen milk by pumping one bottle or so a day. After you've pumped, transfer milk to clean bottles with solid caps or plastic bags made expressly for storing breast milk. If you can't find these bags, Ask Dr. Sears suggests layering together two bottle liner bags to prevent freezer burn. If you're filling each container full, leave an inch of open space at the top of the bottle or bag to allow for the liquid to expand as it freezes. Alternatively, fill each container with a single serving of breast milk. Keep in mind that your baby might be drinking more milk in a few months than he drinks now, so fill containers with an ounce or two more than he currently drinks. Label each bottle with masking tape marked with the date, and tuck the containers into the back of the freezer.
Thawing and Serving Breast Milk
The day before your baby needs your expressed milk, pull out the oldest containers from the freezer. Breast milk will thaw in the refrigerator in 12 to 24 hours. Place it in the back of the refrigerator, since it will be exposed to more warm air in the front or on the door of the fridge. If the milk is still a bit slushy when your infant is hungry, run the bottle under warm water, swirling it often, until the milk is warm. Use this method to warm breast milk from the fridge, or follow your bottle warmer's instructions to heat it that way.
Traveling with Frozen Milk
Packing up frozen breast milk is an easy way to keep your baby fed when he's traveling without you or when feeding him on the go will be a challenge. Outside of your home's freezer, milk won't stay frozen for long. If the journey will be shorter than 12 hours, load the bottles into a cooler with frozen ice packs. Transport fully frozen containers to a traditional freezer, or thaw them for immediate use. If the trip will take longer than 12 hours, the Children's Hospital of Philadelphia recommends packing containers in a foam cooler filled with dry ice. Most airlines will even allow coolers of dry ice as checked or carry-on luggage, provided you carry only a small amount. Check with your airline before flying with frozen breast milk.