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Last updateTue, 28 Oct 2014 9pm

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Breastmilk Storage

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As a mom on the go, there may be times when you will need to express your breastmilk and store it for later use. Returning to work is a prime example of a time when breast expression and milk storage is needed. Learn how to store your milk safely with these tips:

  • Remember to wash your hands thoroughly prior to expressing your milk to reduce the risk of milk contamination. You do not need to wash your breasts or nipples prior to expression.
  • Breastmilk storage containers should be washed in hot, soapy water and thoroughly rinsed or washed in the dishwasher prior to use. Sterilizing is not necessary for healthy babies.
  • Use appropriate containers when storing your breastmilk.
    • The best choice is glass and polypropylene containers which have been shown to best preserve the components of breastmilk.
    • Plastic (polyethylene) storage bags are another option for milk storage. These bags save precious freezer space, but the milk can become contaminated if the integrity of the bag is compromised. To reduce the likelihood of this happening, use sturdy bags and be sure the bag is completely sealed. Keep the bags in a designated area of the freezer and use some type of storage ziplock bag, bowl or container. Special note: If your baby is premature and in the NICU, ask your neonatologist, NICU nurses or lactation consultant if storage bags are appropriate to use at this time. If your baby is ill, they may recommend storage bottles to be on the safe side.
  • Avoid containers made of polycarbonate which contains bisphenol A (BPA), a plasticizer which has gotten much press due to its hormone disrupting activity. BPA can leach from the plastic when heated and can cause neurological, developmental and reproductive harm.
  • Label your storage container with the date of pumping and the amount of milk in the container. Keep in mind that plastic breastmilk storage bags may not measure the milk accurately therefore note the volume amount in your collection bottle before pouring into storage bags. Special Note: If your baby is in the NICU, include the time of pumping on your label.
  • Leave room in the container to allow for the breastmilk to expand during freezing.
  • Freeze your milk in small portions (approximately 2-5 ounce portions) to ease the thawing process and to reduce the likelihood of waste.
  • Store breastmilk in the back of the freezer to avoid warming when freezer door opens. Also keep on a freezer shelve to avoid warming during automated defrost cycles.
  • Use the oldest milk first. This way, you can ensure that your milk will not expire.
  • Once you have thawed breastmilk, do not refreeze it. Use thawed breastmilk within 24 hours.
  • Breastmilk that has been in the refrigerator for less than 48 hours may be frozen.
  • Do not add newly expressed milk to previously stored milk as this will increase the temperature of the already cooled milk. Instead, cool the newly expressed milk and then add the previously stored milk.
Breastmilk storage guidelines vary from source to source. Below is the most current guidelines available for Healthy Term Babies.

Breastmilk Storage Guidelines (For Healthy Term Babies)



Insulated Cooler Bag with Ice Packs


Freezer Inside of Refrigerator

Freezer with Separate Door from Refrigerator

Deep Freezer


60°F -85°F
(16°C -29°C)

(15° C)



0°F to -4°F
(-17°C to -20°C)



Freshly Expressed Breastmilk

3-4 hours (optimal)

         6-8 hours         (acceptable under very clean conditions)

Up to 24 hours 

Less than 72 hours (optimal)

     Up to 8 days        (acceptable under very clean conditions)

2 weeks

3-6 months  (optimal)


Up to 12 months (acceptable)

12 months or longer

Thawed Breastmilk

No more than 3-4 hours*

Up to 8 hours*

Up to 24 hours 

Never refreeze thawed milk

Never refreeze thawed milk

Never refreeze thawed milk

* Not much data available.

Ready to learn how to safely defrost your breastmilk to feed to your baby? Find out in our next segment, "Defrosting Breastmilk".
Academy of Breastfeeding Medicine (2010) ABM Clinical Protocol #8: Human Milk Storage Information for Home Use for Full-Term Infants
Walker, M (2011). Breastfeeding Management for the Clinician (2 edition). Boston: Jones and Bartlett Publishers.
WIC: Storing Your Breastmilk

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