Mothers might express their breast milk for a variety of reasons.
For example, they may express full time because they have a premature baby who is unable to breastfeed well just yet.
They may have returned to work and want to continue to provide their baby with their milk while there.
Maybe they may just want to express to have a store of expressed breast milk (EBM), in case they need to be away from their baby for a period of time.
Regardless of the reason for expressing, there are usually many questions related to the storage of EBM.
Breast Milk Storage
Here are 14 facts and tips about breast milk storage.
Please note that the information about breast milk storage times in this article is based on the guidelines in Australia's National Health and Medical Research Council’s infant feeding guidelines. Storage times vary depending on what source is referred to.
#1: Expressed Breast Milk Can Be Stored At Room Temperature For 6-8 Hours
If the room temperature is up to 26 degrees Celcius (78 degrees Fahrenheit), freshly EBM may be stored for 6-8 hours. In warmer temperatures, bacteria can grow faster, so if the temperature is higher than this, 3-4 hours may be a more reasonable time frame.
#2: EBM Can Be Stored In The Fridge For Up To 72 Hours
Freshly EBM can be stored for at least 72 hours and demonstrate safe levels of bacterial growth. EBM should be stored at the back of the fridge where it is coldest.
#3: Freshly EBM Can Be Stored In The Freezer For 3 Months
Freshly EBM can be stored for 3 months in the freezer section of the fridge with a separate door (-18 degrees Celcius), for 2 weeks in the freezer section of a fridge (-15 degrees Celcius), or for 6-12 months in a defrost deep freezer (-20 degrees Celcius) that is opened infrequently.
White blood cells are destroyed and vitamin C levels in EBM are reduced with freezing. However, total protein, fat, enzymes, lactose, most vitamins, antibodies and other anti-infective factors are generally preserved in EBM with freezing.
#4: Freshly EBM Can Be Added To Previously EBM
In order to prevent accidental rewarming of previously EBM that has been refrigerated, it is best to not add freshly EBM to it.
However, if your are adding EBM together, it is best to first cool down freshly expressed breastmilk in the fridge before adding it to the stored previously EBM.
#5: Some Mother’s Expressed Breast Milk Smells
A few mothers find that their EBM smells fishy, metallic or soapy after storage in the fridge or freezer. This does not mean their EBM has gone off.
The most likely cause is due to the action of the enzyme lipase having broken down fats in the EBM while it has been stored.
The EBM is safe for a baby to drink and the majority of babies drink it without issue. So, if this happens to your EBM and your baby drinks it, then nothing needs to be done.
However, some babies refuse to drink it. If this happens to you, you can prevent the problem by heating your milk in the following way after expressing it (and before storing it) to prevent lipase from taking action:
- Heat your EBM to 72 degrees Celcius for 2 minutes straight after expressing (before storing) to stop lipase from working.
- Thereafter, cool the EBM quickly by putting the container in a bowl of ice and water.
Heating your EBM in this way will mean some of the immune protective factors of it will be reduced or destroyed but it is still better than having to throw it away. The EBM can then be stored as per usual.
#6: EBM Should Not Be Warmed In Microwave
EBM can be warmed by setting it in a container of warm water or running it under warm water.
EBM should not be warmed (or defrosted) in the microwave because it can cause the milk to heat unevenly and it also significantly reduces (or destroys) the anti-infective properties of breastmilk.
#7: Once Feed Has Begun, Any EBM Left Over Must Be Discarded
Once a baby has begun drinking EBM, a degree of bacterial growth occurs in the milk from the baby’s mouth.
Nonetheless, some parents/sources are comfortable using any left-over EBM for one additional feed.
However, since there isn’t strong evidence to support or advise against this practice, discarding any EBM that your baby doesn’t drink within 1-2 hours after he has begun the feed seems reasonable.
An even better idea is to only offer your baby an amount of EBM that you are certain he will finish. This way, there won’t be any left over.
#8: EBM Doesn't Have To Be Warmed Up
A baby can drink EBM that is cool, at room temperature or warmed. Some babies show a preference.
#9: EBM Can Be Defrosted In Fridge
It is best to defrost EBM in the fridge. However, if it needs to be thawed more quickly, its container can be set it in a container of warm water or ran under warm water.
#10: EBM Can Be Stored In Glass Or Plastic Containers, Or Sealable Plastic Bags
There are various options for what to store EBM in. Glass or plastic containers can be used. If sealable plastic bags are used, choose ones that are sturdy, that can be sealed well and store them in an area where damage to the bag is minimised.
#11: Thawed EBM Can Be Stored In The Fridge For Up To 24 hours
EBM that has been thawed in the fridge can be stored for up to 24 hours after thawing.
#12: Thawed EBM Can Be Stored At Room Temperature For Up To 4 Hours
Once thawed, EBM is less able to inhibit the growth of bacteria.
Hence, previously frozen EBM that has been thawed for 24 hours shouldn’t be left out at room temperature for more than 4 hours.
#13: There Is Insufficient Evidence About Re-freezing Or Re-warming EBM
At this point in time, there are no recommendations that can be made with regards to re-freezing or re-warming EBM.
#14: There Is No Evidence That EBM Needs To Be Discarded If A Mother Has A Breast Or Nipple Infection
A mother might be worried that any milk she expresses while she has nipple thrush or a bacterial nipple infection might be contaminated.
However, there is no evidence that a mother who has breast or nipple pain from what is considered a bacterial or fungal (thrush) infection needs to discard her EBM.
Uncontaminated EBM naturally contains healthy bacteria (probiotics) that is important to help established a baby’s gut flora. Probiotics create conditions in the gut that help retard the growth of unhealthy bacteria.
As mentioned, guidelines may vary depending on the source. As always, you can compare sources and choose what feels right for you and your baby.