Guidelines for storing, freezing and thawing human milk
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. Vessels must be sterile prior to use. If freezing the milk is intended, we recommend polypropylene or glass bottles - robust, convenient and economical breast milk containers. Ensure that you date and label the bottles after use. Do not fill past the top of the bottle filling scale in order to allow for expansion of the milk. When using glass bottles for the first time, it's worth loosening the cap a little before freezing and screwing down fully after the milk has frozen and expanded.
Disposable bags may also be used. Ensure that these have been designed specifically for storing breast milk.
We are a business, be aware that there are other brands of bottle in addition to those which we stock.
Storing, freezing and thawing expressed 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. Ideally use within 4 hours (La Leche League International).
Once your baby has drunk from a container of breast milk that has been heated to body temperature (98°F, 37°C), it must be used within an hour or thrown away (The Breastfeeding Network).
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 (NHS Choices, NCT).
Breast milk can be stored in a fridge with a temperature of between +5-10°C for up to 3 days. (The Breastfeeding 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 compartment within a refrigerator
Breast milk can be stored in a freezer (ice) compartment with a temperature of -15°C (or lower) for up to 2 weeks (La Leche League International, NHS Choices).
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 Breastfeeding Network, NHS Choices and NCT advocate that breast milk can be stored for up to six months in a freezer that has a constant temperature of -18°C or lower. La Leche League International suggest that 6-12 months or longer is usually safe, but that some of the fats break down over time.
Whilst technically possible to store expressed breast milk for extended periods, it is important to remember that your breast milk composition changes naturally over time. Human milk expressed by mothers who have been lactating for over a year has increased fat and energy content compared to women who have been lactating for less time (Kellymom). Considering this, I therefore recommend that frozen breast milk should ideally be used in date order and as soon as is practical after expressing.
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 between 12 hours of removing from the freezer (The Breasteeding Network) and 24 hours (La Leche League International).
If defrosted breast milk is allowed to warm to 'room-temperature', it needs to be used or thrown away (NCT). Freezing milk in smaller containers (for example, Sterifeed 50ml bottles) will minimise such waste.
Do not use a microwave to defrost breast milk. Thawed breast milk must never be re-frozen (NCT).
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'. According to La Leche League International, microwaving may cause the loss of some of the beneficial properties of the milk.
As a UK Health Professional, an associate of a United Kingdom based company, and following local practices, it is my view that breast milk collection and storage media must be sterilised prior to use.
However, opinions vary, and in some regions, washing equipment with hot water and detergent is considered acceptable. If in any doubt, consult your preferred local Healthcare Professional.
Secondhand equipment MUST be thoroughly sterilised prior to use.
Some breastpumps can ingest milk via the collection set tubes if the collection bottle is over-filled or tilted during expressing. Of those (open system) pumps, only a few models can be cleaned out. Milk drawn into the pump motor which is returned to the bottle may be contaminated. If in any doubt, discard the milk.
The National Childbirth Trust (NCT) - 'How to express and store your breastmilk', accessed October 2014 www.nct.org.uk
NHS Choices - 'Expressing and storing breast milk', accessed October 2014 www.nhs.uk
The Breastfeeding Network (BFN) - 'Expressing and storing', accessed October 2014 www.breastfeedingnetwork.org.uk
La Leche League International - 'What are the LLLI guidelines for storing my pumped milk?', accessed October 2014 La Leche League International
Kellymom - 'Breastfeeding Past Infancy: Fact Sheet', accessed October 2014 Kellymom.com
This guide © Janette Cassidy BSc (Hons), RGN, DN, HV, Specialist Practitioner (Public Health), all rights reserved.