Safe storage and handling of breast milk

Storage containers

It's best to store breast milk in glass or hard plastic containers. For healthy term infants, wash containers in hot soapy water, rinse in hot water and allow to air dry. After cleaning and drying, store them in a covered container so that they remain clean and ready to use.

If you choose to store your milk in disposable plastic freezer bags, make sure the bags are designed for breast milk storage (individually sterilized), and use them for short-term storage only. Breast milk may lose some of its immune properties when stored in plastic bags. This shouldn’t be a problem for a healthy baby who only occasionally gets breast milk that has been frozen in plastic bags.

Storing fresh breast milk

Fresh expressed breast milk should be stored in small amounts of 30 to 60 mL (2 to 4 oz.) and labelled with the date and time. It is safe to add freshly expressed breast milk to the milk you have expressed earlier on the same day. However, combining the milks together must be done only after the milk has cooled down. Your breast milk will stay good for:

• 6 to 8 hours at room temperature (less than 25°C) OR
• 24 hours in an insulated cooler with ice pack OR
• 5 days at the back of the refrigerator (≤ 4°C or 40°F) for healthy full-term babies

Please note: If you don’t plan to use your breast milk within 5 days after expressing it, freeze it immediately.

When you’re ready to use your fresh expressed breast milk, be sure to check the date on the container to make sure that it hasn’t expired; always use the milk with the oldest date first. You can warm the milk in any of the following ways:

• Run the milk container under warm water in the sink.
• Put the milk container in a bowl of warm water.
• Put your milk container in a bottle warmer.

Make sure you always check the temperature of the milk before feeding it to your baby.

Freezing breast milk

You can freeze breast milk in small amounts of 30 to 60 mL (2 to 4 oz.) once it has cooled down. Your breast milk must be in an appropriate container and must labeled with the date it was expressed. Leave at least one inch of space at the top of the storage container or the appropriate freezer bag because your breast milk will expand when frozen.

Your breast milk will stay good for:

• 3 to 6 months when at the back of the freezer of a refrigerator (–18°C or 0°F) OR
• 6 to 12 months in chest or upright freezer (–20°C or –4°F)

Take note that the less frequently your freezer door is opened, the longer you can store your breast milk. When you are ready to use your frozen breast milk, make sure you safely thaw the milk. You must:

• Check the date on the container to make sure that it hasn’t expired; always use the milk with the oldest date first.
• Thaw the milk under warm running water or in the refrigerator. NEVER thaw breast milk at room temperature.
• Use the milk within 24 hours of taking it out of the freezer. NEVER refreeze previously thawed breast milk.
• Warm the thawed breast milk by placing it in a bowl of warm water. Milk is to NEVER be warmed up in a microwave and must be used within one hour of being heated.
• Always check the temperature of the milk before feeding it to your baby.

Please note that early premature babies (born before 34 weeks gestation) and late preterm babies (born between 34 and 37 weeks gestation) require special precautions for safe storage and handling of breast milk. Consult with your primary healthcare provider if you have any questions.

Adapted with permission from Ottawa Public Health.