Storing, Freezing and Thawing Expressed Breast Milk

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A brief summary by Jeanette Cassidy BSc (Hons), RGN, DN, HV, Specialist Practitioner (Public Health)

January 2008.

There is no disputing that ‘breast is best’, but for some of us (the author included), breast feeding is not always possible.

By expressing (pumping), a mother ensures that her baby receives all of the benefits of breast milk, even if she is unable to breast feed, is away from her baby or perhaps has returned to full-time work.

There is conflicting (but well-researched) advice available regarding the storage of mother’s expressed breast milk.

In light of this, we have adopted what we consider to be the safest and easiest guidelines for a mum to follow.

Breast milk can either be stored in purpose-made bottles or bags.

If freezing the milk is intended, we recommend the Axifeed range of bottles as the most robust, convenient and economical breast milk container.

Ensure that you date and label the bottles after use. Also, do not fill past the top scale of the bottle in order to allow for expansion of the milk.

If using disposable bags, ensure that these have been designed specifically for storing breast milk.

Human milk can be stored in 3 ways.

Whichever method you use, ensure that you label the container with date and time of expression and always use the oldest milk first.

Storage at room temperature (68°F, 20°C max)

Freshly expressed breast milk can be kept at room temperature for a maximum of 6 hours (The Breast Feeding Network).

Breast milk that has been heated to body temperature (98°F, 37°C) must be used within an hour.

Storage in a refrigerator

Breast milk can be stored in a fridge with a temperature of between +2-4°C for up to 5 days (Unicef).

Breast milk can be stored in a fridge with a temperature of between +5-10°C for up to 3 days. (Breast Feeding Network).

Use a fridge thermometer to check the temperature of your fridge regularly.

Your milk should not be stored in the door of a fridge as the temperature of the expressed breast milk will fluctuate as the fridge door is opened. The best place is in a covered drawer in the fridge. You can then ensure that the drawer is only opened when you need to remove or store more breast milk.

Where there is no drawer available, store in the lowest part of the fridge towards the back.

Storage in a freezer/deep freeze*

*These guidelines DO NOT refer to the small freezer compartment within a standard refrigerator.

If you intend to freeze unused breast milk, freezing should take place within 24 hours of expressing.

The Breast Feeding Network (BFN) advocates that breast milk can be stored for up to six months in a freezer that has a constant temperature of -18°C or lower.

However, Unicef’s "Breastfeeding Your Baby" document advises that breast milk can be kept in a freezer for just 3 months.

It is important to remember that in order to meet your baby's nutritional needs, your breast milk composition changes naturally in line with your baby’s growth.

Considering this, I therefore recommend that frozen breast milk should ideally be used within 3 months of expression.

Defrosting breast milk

The safest way to defrost is to transfer the breast milk container to a refrigerator and allow the milk to thaw overnight. If the container remains in the fridge, the milk should be used within 24 hours of thawing (LaLeche).

Frozen breast milk which has been defrosted outside of the fridge but then placed back in the fridge once in a liquid state should be used within 4 hours (LaLeche).

If defrosted breast milk is allowed to warm to 'room-temperature' (68°F), it needs to be used immediately (BFN).

Do not use a microwave to defrost breast milk. Breast milk must never be re-frozen.

Warming the milk

The safest way to warm up your breast milk is to place the storage bag or bottle into a bowl of warm water, first ensuring that the bag or bottle is properly sealed.

Never use a microwave oven, since microwaving can cause uneven temperatures, including 'hot spots'.

In addition, I am unable to find conclusive research on the negative/positive effects of microwaving human breast milk at this time.


As an associate of a United Kingdom based company, and following local practices, I strongly recommend that breast milk collection and storage media are sterilised prior to use.

However, opinions vary, and in some regions, washing equipment with warm water and detergent is considered perfectly acceptable.

If in any doubt, consult your preferred Healthcare Professional.

Secondhand equipment MUST be thoroughly sterilised prior to use.



The Breastfeeding Network (BFN) - 'Expressing and Storing Breast Milk' - Sept 2006
Unicef & UK Baby Friendly Initiative - 'Breastfeeding Your Baby' -
LaLeche Leage Great Britain - 'Storing Human Milk' 1998 Cat. 0724

This guide ©Copyright Jeanette Cassidy 2008.

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