If you’re a pumping mama, spilt milk can give you plenty to cry about. It takes a Herculean effort to follow safe storage rules when half asleep after a 3 a.m. pumping session or running late for a 10 a.m. meeting. But, little details matter. Shortchanging and cutting corners could make your baby very sick.
Here are the basics when it comes to storing your liquid gold safely.
Breast milk storage guidelines
The guidelines for storing and preparing breast milk for healthy, full-term babies depend on a few factors: the type of breast milk, the storage location and the temperature. If all of this information (see chart below) is hard for you to remember on the fly, think “rule of fours”: For freshly pumped breast milk, you can safely give it to baby for up to four hours at room temperature and up to four days in the refrigerator.
To prevent your breast milk from going to waste, store it in small batches; 2 to 4 ounces (59.1 to 118.2 milliliters) is recommended. Any remaining breast milk left in a bottle after your baby is finished with a feeding should be used within two hours, or, if quickly refrigerated, used for the next feeding.
You can always thaw an extra container if needed — and you have some options in terms of container type:
- Sterile glass or hard BPA-free plastic bottles with tight-fitting lids. Do not use containers with the recycle number 3 or 7, which may contain Bisphenol A (BPA).
- Breast milk storage bags made for freezing human milk. Do not use disposable bottle liners or other plastic bags to store breast milk; they are too thin and could sprout a leak. In addition, there is considerably higher fat loss when milk is stored in these polyethylene bags.
Note: Breast pumps and supplies that assist lactation qualify as tax-deductible breastfeeding gear. The IRS doesn’t provide a specific list of approved items beyond the pump itself, but if the product was used for a medical reason (e.g., cream on your cracked nipples), it will likely qualify as a tax-deductible item. Also keep track of what you spend and check your insurance policy to see if your plan covers breastfeeding supplies, such as storage bags, in addition to breast pumps.
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How long does breast milk last at room temperature?
The length of time breast milk can last at room temperature depends on its type.
- Freshly pumped breast milk can be stored at room temperature (no warmer than 77° F) for up to four hours if it’s not in direct sunlight or close to other sources of heat.
- Thawed, previously frozen breast milk can stay at room temperature for one to two hours. Use it or lose it!
If your baby has some leftovers after a feeding and didn’t finish the bottle, it must be used within two hours. After this time, you must discard it. Too many germs!
Storing breast milk in smaller quantities so that your baby uses the full portion at each feeding can help reduce waste.
How long does breast milk last in the fridge?
The amount of time breast milk can stay in the fridge depends on the type:
- Freshly pumped breast milk can be stored in the back of the refrigerator (39° F or 4° C) for up to four days — just don’t forget it’s back there.
- Thawed, previously frozen breast milk can stay in the refrigerator for 24 hours before you have to throw it out. (No mom wants that!) So, only take out what you think your little one will need for a day. Never refreeze breast milk after it has been thawed.
Again, if your baby has some leftovers after the feeding, it must be used within two hours.
When warming breast milk from the fridge, place the bottle in a bowl of warm water or run it under warm water. Microwaving breast milk is not safe.
Breast milk naturally separates into a milk layer and a cream top when it is stored. It looks a little funky, but it’s normal and is safe to swirl prior to feeding.
How long does breast milk last in the freezer?
You can store breast milk in a refrigerator with a freezer that has a separate door (0°F or −18°C) for up to 12 months, although using it within six months is preferable.
The earlier you use up your breast milk, the better, because longer storage can diminish the amount of vitamin C in it. The temperature of your freezer should be around 0° F. Again, like the fridge, it’s best to store it in the back of the freezer furthest away from the door where temperatures are most consistent.
Some women produce large volumes of breast milk to freeze, while other women never seem to produce enough. When it comes to freezer storage, however, smaller portions are actually better. Portions that are 2- to 4-ounce (59.1 to 118.2 milliliters) are recommended to not waste any.
Make sure to label the bottles, cups or bags with the date and leave an inch or so from the milk to the top of the container. (Breast milk expands as it freezes, so wait to tighten bottle caps or lids until the milk is completely frozen.)
How should you thaw frozen breast milk?
The safest way to thaw breast milk is in the refrigerator overnight. You can also hold the bottle or bag under warm running water or set it in a container of warm water.
Remember that heating breast milk in the microwave or boiling it is not safe. These methods can cause loss of nutritional properties of breast milk and could be unevenly hot, making it dangerous for your baby to drink. Once previously frozen breast milk is thawed, it can be stored in the fridge and must be used within 24 hours.
Note: Thawed breast milk can smell and look different from fresh breast milk when a mom’s breast milk has excess lipase activity, also known as high lipase breast milk. If your baby doesn't want to drink the thawed breast milk, talk with your doctor about ways to help neutralize the enzyme and lessen the smell.
Breast milk storage for NICU and hospitalized babies
If your baby is in the NICU or is hospitalized for other reasons, your breast milk can be fed to her through a tube that passes through the nose or mouth into the stomach or from a tiny cup or bottle. The feeding route depends on your child’s condition and on the policies at your hospital.
The traditional breast milk storage guidelines (above) were written for healthy, full-term babies. Storage guidelines are stricter for babies who are hospitalized and have weaker immune systems. Here are some general things to keep in mind:
- The label on your breast milk container should include your baby's name, the date, the time of day you pumped and any medicines or substances you’ve taken or been exposed to since the last pumping session.
- Freshly pumped breast milk for premature or hospitalized infants should be used within one hour or refrigerated. The bacterial growth that occurs in breast milk left out at room temperature can be dangerous to them, and it’s better to be safe. If storing it in a fridge, the freshly pumped breast milk is good for up to 48 hours. Dedicated refrigerators and freezers are provided for breast milk storage in the hospital.
- Thawed, previously frozen breast milk must be used within 24 hours (if thawed in the refrigerator) or two hours (if warmed) or it must be discarded. It is safe to give breast milk that has been thawed for 24 to 48 hours after your baby comes home from the hospital.
Always discuss the recommended storage guidelines for your situation with your baby's healthcare providers. They may have more specific instructions for you to follow at their hospital.
How to tell if you shouldn’t use stored breast milk
If you know what rotten milk smells like then you’ll probably know what rotten breast milk smells like. If you still aren’t sure, try tasting it. If sour, then it’s bad and needs to be tossed.
Another trick? Watch how the breast milk moves. When breast milk is still good, it mixes back together easily with a gentle swirl of the bottle. If it doesn’t do this or has chunks floating in it (like regular milk does when it’s bad), throw it out.
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