Many mothers have questions about safe breast milk storage. It can be confusing with so many different recommendations out there.
The most simple guideline for fresh breast milk storage is the Rule of 5:
Room Temperature (60-85 F): 5 hours
Refrigerator (39 F): 5 days
Freezer (0 F): 5 months
Previously frozen breast milk will stay fresh in refrigerator for 24 hours after thawing.
These are optimal breast milk storage guidelines (similar to the “best by” date on food products). Give premature or sick babies breast milk based on these guidelines.
What should I do with older breast milk?
Although you should make every effort to use expressed milk within the optimal time frame, if you have a healthy baby, breast milk is acceptable for use for 6-8 hours at room temperature, 5-8 days in a refrigerator, and 6-12 months in a deep freezer. If you are unsure if breast milk has spoiled, try smelling it. It should smell sweet, without a strong odor.
If you find that you have too much stored milk, consider donating your milk before it becomes to old to use. Your donation could make a big difference for a premature baby. Some mothers add old breast milk to their baby’s bathwater instead of throwing it away.
Unfinished bottles of expressed breast milk
Try to store your expressed breast milk in feeding size amounts to avoid wasting. Despite your best efforts, there may be times when your baby leaves milk in the bottle after a feeding. In this situation, we have no research studies on which to base recommendations. We know that once a baby starts to drink from a bottle, baby’s mouth transfers some additional bacteria into the milk. If a baby is premature, or has special health problems, it is best to discard any milk left over at the end of a feeding. However, many mothers of term babies refrigerate the milk and feed it to the baby at the very next feeding before any new milk is offered. If you decide to do this, verify that the milk has not spoiled by smelling it before giving it to your baby.
Separation of breast milk during storage
When any fresh milk sits, a layer of fat or “cream” forms on the top. The same is true for breast milk. This does not mean the milk has spoiled! Prior to feeding, simply immerse the container of milk in warm water to reheat it. Then, gently swirl the milk to mix in the fat before feeding it to your baby.
Very rarely, some mothers find that their expressed breast milk develops a soap-like flavor. This can be caused by excess lipase in the milk, among other reasons. You can find more information about excessive lipase here. I recommend mothers check the taste of their milk before storing large quantities of milk for future use.
In 2010, the Academy of Breastfeeding Medicine published an updated protocol with evidence-based recommendations for the storage of human milk for term infants. The protocol contains useful information and answers many common questions about breast milk storage.