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A Comprehensive Guide to Breast Milk Storage

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Now that you’ve gone through the general unpleasantness of pumping your baby’s liquid gold – there are a million questions that come up about how best to store it.


As a general rule, if you think that a bottle is going to be used in the next 3-6 days you are better off storing the milk in a bottle in the refrigerator. I recommend against transferring to a milk storage bag for refrigerator storage since the milk will separate in the fridge and the all-important fat will likely get stuck to the sides of the bag and lost when you transfer the milk to a bottle for your baby to drink. If you think its unlikely to be used within six days, you should transfer the milk to a milk storage bag immediately after pumping and put it directly in the freezer. Putting the milk directly in the freezer avoids allowing the milk to separate in the fridge and will yield a more nutrient rich milk to your baby when she is ready to drink it. If you expect your baby to drink the milk in the next 4-6 hours, you should consider just leaving the milk out at room temperature since that way you don’t have to worry about the milk separating in the fridge.


Store your milk in disposable bags specifically designed for breastmilk, leaving some extra room so the container won’t burst. I like the Lansinoh brand personally, because the double seal at the top greatly reduced the number of spills I experienced. Make sure to label each bag with the date and amount of milk. Freeze in 2-5 oz portions, as small amounts will thaw quicker. Also, you’ll have to thaw the whole bag at the same time so if you freeze a large quantity at once it may be harder to use when you thaw it (and you can’t refreeze milk). Never add freshly pumped milk to frozen milk (you can cool freshly pumped milk in the fridge and then add it to frozen milk, just don’t add warm milk to the frozen milk directly).

You should always put the bags in the freezer flat so they will be easier to store. I recommend using a storage system that flattens the milk while it freezes and then when it gets full removing all of the bags from the system and storing them together in a large ziplock back labeled with the date range of the milk inside. It is always better to freeze milk in the main part of the freezer rather than the door. Milk can stay good in the freezer for up to 6 months.


There are two main methods that you can thaw milk: (1) thaw it straight from the freezer when you are ready to use it; or (2) put it in the refrigerator the day before you want to use it. The first method maintains the most nutrients in the milk since you aren’t going to lose the fat sticking to the sides of the bag in the fridge but it takes the longest to get the bottle ready (and with a screaming baby waiting for the milk to thaw five minutes might as well be an eternity).

To actually thaw the milk, you can use a bottle warmer or the good old fashioned sink with warm water. NEVER put milk in the microwave since it can create hot spots that can burn your baby – even if the milk you test on your wrist is a comfortable temperature. Make sure that the milk in the bottle is remixed (with the fat from the sides of the bottle reintegrated into the liquid milk) before you serve it. People used to recommend gently swirling the milk but it has been proven that shaking the milk does not harm it and it is much more efficient at remixing it. Once you have thawed milk you can not refreeze it. If your baby doesn’t finish a bottle that has already been thawed and warmed, it is safe to refrigerate and use again within a few hours.


When a baby drinks from a bottle the germs from their mouth can make the milk go bad more quickly. If they don’t finish it, you can still use the bottle for their next feeding but you MUST put it in the refrigerator when they have finished eating what they are going to eat from the bottle. Don’t let it sit out. There is conflicting advice on how long the refrigerated bottle will last but shorter than 2 hours is universally considered still good.


Play the “Is Your Milk Still Good” Game:

-Quick guide chart below:





Marylynne Schwartz is a mom, wife, newly minted entrepreneur, recovering attorney and community enthusiast. I look forward to sharing my parental musings with you as well as insider tips into making the most of (aka surviving) kid-centric things to do in Chicago.

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