Pumping breast milk is a common practice for many new mothers. It allows them to store breast milk so that someone else can feed the baby while mom is away. However, there are guidelines for how long pumped breast milk can safely sit out before it needs to be stored. Here is a quick overview of how long pumped breast milk can be kept at different temperatures:
Quick Answers
- Room temperature: Up to 4 hours
- Insulated cooler bag: Up to 24 hours
- Refrigerator: Up to 4 days
- Freezer: Up to 6 months in a deep freezer, 3-6 months in a refrigerator freezer
Read on for more details on how to store pumped breast milk safely and how long it lasts at different temperatures.
Room Temperature
Freshly pumped breast milk can sit out at room temperature for up to 4 hours. Room temperature is defined as up to 77°F (25°C). After 4 hours at room temperature, the milk needs to be stored in the refrigerator or freezer.
Some key room temperature guidelines include:
- Pumped milk should not sit out for more than 4 hours total, including the time spent pumping and preparing the milk for storage.
- Any milk that baby drinks directly from the breast does not need to be refrigerated.
- It’s best to refrigerate or freeze milk right after pumping if possible.
Bacteria can start to grow quickly in milk left out at room temperature. So keeping the total time at room temperature short limits potential bacterial growth.
Insulated Cooler Bag
An insulated cooler bag with ice packs can keep pumped milk cold when transporting or storing for short periods. Milk can be kept in an insulated cooler bag for up to 24 hours.
Guidelines for storing in an insulated cooler bag:
- The cooler should be kept as cold as possible, best around 39°F (4°C).
- Replenish ice packs as needed to maintain cold temperature.
- Store milk toward the bottom of the bag rather than near the opening.
- Limit opening the bag as much as possible.
- After 24 hours, transfer milk to the refrigerator or freezer.
An insulated cooler is great for transporting milk short distances, such as from home to daycare. It allows you to keep pumped milk cold for up to a day when refrigeration is not available.
Refrigerator
Refrigerating pumped breast milk is the most common way to store it. Milk can be kept refrigerated for 3-4 days.
Guidelines for refrigerated storage:
- Store milk toward the back of the refrigerator, not on the door.
- Keep temperature at 39°F (4°C) or colder.
- Put milk in the back where it is coldest.
- Store milk in sealed containers, never open containers.
- Use oldest milk first, newly pumped milk toward the back.
Properly stored in the refrigerator, breast milk retains its nutritional and immunological properties for around 4 days. After that, it is recommended to freeze the milk.
Thawing Refrigerated Milk
Milk that has been thawed in the refrigerator can sit out at room temperature for up to 4 hours before it needs to be used. Do not return thawed milk to the refrigerator for storage. Only re-freeze milk if it still contains ice crystals.
Freezer
Freezing breast milk allows it to be stored for the longest durations. How long it lasts depends on the type of freezer.
- Deep freezer (-4°F / -20°C): 6-12 months
- Refrigerator freezer (5°F / -15°C): 3-6 months
- Chest or upright deep freezer (-4°F / -20°C): 6-12 months
Tips for best freezing results:
- Leave 1/2 inch space at the top of containers for expansion.
- Store milk toward the back of the freezer where temperature is most stable.
- Avoid repeated freeze-thaw cycles. Thaw only what you need.
- Keep frozen milk away from freezer doors/walls which are warmer.
- If possible, newly pumped milk can be added to already frozen milk.
Well frozen and thawed milk retains its nutrients and antibodies. The fats in breast milk may separate and cling to the bottle after thawing but can be mixed back in.
Thawing Frozen Milk
There are a few options for safely thawing frozen breast milk:
- Refrigerator: Thaw overnight in the fridge. Use within 24 hours.
- Lukewarm water: Submerge bottle in lukewarm water. Use within 2 hours.
- Gradual warming: Place bottle under warm running water or in a bottle warmer. Use immediately.
- Never thaw at room temperature or in hot water which can breed bacteria.
Avoid re-freezing thawed milk more than once, as this can impact quality and nutrient composition. Only re-freeze if ice crystals are still present.
Other Storage Situations
There are a few other short-term scenarios where pumped breast milk can be kept unrefrigerated or without freezing:
Babies on Occasional Formula
If baby sometimes gets formula but mostly breastfeeds, pumped milk can sit at room temperature while feeding baby formula. Once formula is given, the milk should be used within 2 hours or discarded.
Nighttime Feeding
Some moms prefer not to go to the kitchen late at night. Pumped milk can be kept at room temperature overnight for a maximum of 8 hours for night feedings.
Healthy Full-Term Babies
The above guidelines are conservative recommendations for optimal milk preservation. For healthy full-term babies, milk may be fine for occasional use after 4 hours room temp or 24 hours fridge. But maximum preservation follows the recommend time limits.
How to Know if Breast Milk is Bad
Checking for signs of spoilage is important when using stored breast milk. Here are the signs pumped milk may be spoiled and should be discarded:
- Smells soapy or rancid
- Changes in color or texture – separation, clumps, sliminess
- Curdled appearance
Normal breast milk should be white or cream in color with a mild, sweet scent. Always do a sight and smell check before feeding baby with stored milk.
Proper Storage Containers
To safely preserve breast milk, it must be pumped and stored in proper containers. Here are the best containers for storing pumped milk:
- BPA-free plastic bottles with tight fitting lids
- BPA-free breastmilk storage bags
- Glass bottles with tight sealing lids
Avoid containers with BPA or those not designed specifically for breastmilk like some plastic bags, formula bottles, or food containers. Always use clean containers washed in hot soapy water and air dried.
Preparing to Pump and Store
Proper handling when pumping, transporting, and storing milk helps maximize how long it stays fresh and nutritional. Here are some tips:
- Always wash hands before handling pump parts and bottles.
- Clean pump parts after each use.
- Pump milk in a clean, designated space.
- Label milk with date it was pumped and child’s name.
- Have storage bottles and bags ready before pumping.
- Transport milk in an insulated bag with ice packs.
- Go from room temperature to fridge to freezer as soon as possible.
Take Away Tips
- 4 hours room temperature
- 24 hours in a cooler
- 3-4 days refrigerator
- 6-12 months frozen
- Store milk in back of refrigerator or freezer
- Never re-freeze thawed milk more than once
Follow these storage time recommendations and best practices for refrigerating and freezing to get the most out of your pumped breast milk while keeping it safe for baby!
Frequently Asked Questions
1. Does breast milk expire?
Yes, breast milk does expire and has a limited timeframe for safe use. How long it lasts depends on storage conditions. Room temperature milk should be used within 4 hours. Refrigerated milk lasts 3-4 days. Frozen milk remains usable for 6-12 months depending on freezer type.
2. Can you mix fresh breast milk with frozen milk?
Yes, newly pumped fresh breast milk can be added to already frozen milk. The newly added milk will take on the “freshness” of the frozen milk, which is fine for storage but reduces the shelf life compared to freshly pumped milk.
3. Is it OK to pump directly into storage bags?
Yes, you can pump milk directly into storage bags. Be sure to only use breastmilk storage bags specifically designed for pumping and freezing milk. Lay the bags flat in the refrigerator or freezer for stability.
4. Can you freeze breast milk in glass bottles?
Glass bottles are not recommended for freezing breast milk if they have rubber seals. The rubber can become damaged by the expansion during freezing. However, some glass storage bottles are designed specifically for freezing and can be safely used.
5. Can you add freshly pumped milk to refrigerated milk?
It’s best not to mix fresh milk with refrigerated milk, as it reduces the shelf life of the refrigerated milk. Try to use the refrigerated milk first within 4 days before adding the new milk.
Conclusion
Following proper storage guidelines allows you to safely save breast milk for feedings when you are away from baby. Room temperature and insulated cooler storage provide options for transport and short-term storage. Refrigerating gives you several days of storage, while freezing allows storage for months. With the right techniques, containers, and storage times, you can preserve your breast milk to provide your baby with the ultimate nutrition.