Storing Pumped Breast Milk: Time Limits and Safe Steps

Going back to work, a night out or your partner joining in with feeds: there are many reasons to pump. Every drop you pump is precious, and storing it correctly keeps it safe for your baby. This guide brings together recommendations from the US Centers for Disease Control and Prevention (CDC) and the UK's National Health Service (NHS).

Cleanliness first: The CDC recommends washing your hands well with soap and water before pumping and before preparing milk. The NHS also reminds you that the pump and storage container should be clean and sterilized before each use.

Storage times (CDC):

• Room temperature (25°C (77°F) or cooler): Up to 4 hours
• Fridge: Up to 4 days
• Freezer: About 6 months is best; up to 12 months is acceptable
• Insulated cooler bag with ice packs: Up to 24 hours when traveling

These times are based on recommendations for healthy, full-term babies at home. The CDC also notes that milk quality may decline over time.

There are small differences between organizations: The NHS allows storage for up to 8 days at the back of a fridge at 4°C (39°F) or colder; if you are not sure of your fridge's temperature, this drops to 3 days. According to the NHS, milk can be stored for 2 weeks in the ice compartment of a fridge and for up to 6 months in a freezer at -18°C (0°F) or colder. If the different numbers confuse you, going by the shorter time is the most cautious approach.

Containers and labels:

• Use breast milk storage bags or clean, food-grade containers with tight-fitting lids.
• Do not use disposable bottle liners for storage.
• Clearly write the date you pumped the milk on each container.
• Store milk in small amounts so none goes to waste: about 60-120 ml (2-4 oz), or as much as your baby drinks in one feed.
• When freezing, leave about 2.5 cm (1 inch) of space at the top of the container; milk expands as it freezes.
• Place milk at the back of the fridge or freezer, not on the door shelf.

Thawing: The CDC recommends always using the oldest milk first. You can thaw frozen milk by:

• Moving it to the fridge the night before
• Setting the closed container in a bowl of warm water
• Holding it under warm running water

The NHS says slow thawing in the fridge is best when possible.

No microwave: The CDC and NHS are clear that breast milk should not be thawed or warmed in the microwave. Microwaves create unevenly heated hot spots in the milk that can burn your baby's mouth; according to the CDC, they also damage some of the milk's nutrients. The NHS also advises not warming milk on the stove.

Warming: If you want to warm the milk, the CDC recommends setting the closed container in a bowl of warm water or holding it under warm, but not hot, running water for a few minutes.

How long does thawed milk last? According to the CDC:

• Use milk thawed in the fridge within 24 hours.
• Use milk that has come to room temperature or been warmed within 2 hours.
• Never refreeze thawed milk.
• When your baby finishes drinking, use any milk left in the bottle within 2 hours at most, then throw it away.

The NHS recommends using thawed milk right away and throwing away milk your baby does not finish within 1 hour. The fat in stored milk may separate; the CDC recommends gently swirling the container to mix it.

Quick summary (CDC):

• 4 hours at room temperature
• 4 days in the fridge
• Ideally 6 months in the freezer, 12 months at most
• 24 hours in the fridge after thawing, 2 hours after warming
• Milk your baby does not finish: 2 hours (1 hour according to the NHS)
• Thawed milk is not refrozen

Posting this list on the fridge door can make things easier.

When should you talk to a health professional? If your baby was born early or is in the hospital, storage rules may be different; in that case, follow the recommendations of your baby's care team. For questions about pumping and breastfeeding, you can reach out to your family doctor or a lactation consultant.

Dear mom, the milk you pump is your hard work for your baby in its purest form. Once you set up a simple routine, with clean containers, date labels and the right time limits, that hard work will not go to waste. Give yourself this ease, too.