Breast milk storage: Tips for storing breast milk

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Breast milk storage: Tips for storing breast milk

If you're breast-feeding your baby and going back to work or looking for more flexibility, you're probably considering using a breast pump. Once you start pumping, it's important to know how to safely and properly store your expressed breast milk. Consider these do's and don'ts for breast milk storage.

What kind of container should I use to store expressed breast milk?

Store expressed breast milk in capped glass or plastic containers that have been cleaned in a dishwasher or washed in hot, soapy water and thoroughly rinsed. Consider boiling containers after washing them if the quality of your water supply is questionable.

If you plan to store breast milk for three days or less, you can also use a plastic bag designed for milk collection and storage. While economical, plastic bags aren't recommended for long-term breast milk storage because they may spill, leak and become contaminated more easily than hard-sided containers. Also, certain components of breast milk may adhere to the soft plastic bags during long-term breast milk storage, which could deprive your baby of essential nutrients. If you use breast milk storage bags, place them in containers for greater protection in the refrigerator and freezer.

What's the best way to store expressed breast milk?

You can store expressed breast milk in the refrigerator or freezer.

Always wash your hands before handling expressed breast milk. Using waterproof labels and ink, label each container with the date and time of your earliest contribution. If you're storing expressed breast milk at your baby's child care facility, include your baby's name on the label. Place the containers in the back of the refrigerator or freezer, where the temperature is the coolest.

To minimize waste, fill individual containers with the amount of milk your baby will need for one feeding. You might start with 2 to 4 ounces (59 to 118 milliliters), and then adjust as needed. Also consider storing smaller portions — 1 to 2 ounces (30 to 59 milliliters) — for unexpected situations or delays in regular feedings. Keep in mind that breast milk expands as it freezes, so don't fill containers to the brim.

Can I add freshly expressed breast milk to already stored milk?

You can add freshly expressed breast milk to refrigerated or frozen milk you expressed earlier in the same day. However, be sure to cool the freshly expressed breast milk in the refrigerator or a cooler with ice packs for at least one hour before adding it to previously chilled milk. Don't add warm breast milk to frozen breast milk because it will cause the frozen milk to partially thaw. Keep milk expressed on different days in separate containers.

How long does expressed breast milk keep?

How long you can safely keep expressed breast milk depends on the storage method. Consider these general guidelines:

  • Milk stored at room temperature. Freshly expressed breast milk can be kept at room temperature — up to 77 F (25 C) — for six to eight hours. If you won't use the milk that quickly, store it in the refrigerator or freezer.
  • Milk stored in an insulated cooler. Freshly expressed breast milk can be stored in an insulated cooler with ice packs for up to one day. Then use the milk or transfer the containers to the refrigerator or freezer.
  • Milk stored in the refrigerator. Breast milk can be stored in the refrigerator at 39 F (4 C) for up to eight days.
  • Milk stored in the freezer. Breast milk can be stored in a freezer compartment inside the refrigerator at 5 F (-15 C) for two weeks. If your freezer has a separate door and a temperature of 0 F (-18 C), breast milk can be stored for three to six months. If you have a deep freezer that's opened infrequently and has a temperature of -4 F (-20 C), breast milk can be stored for six to 12 months.

Some research suggests that the longer you store breast milk — whether in the refrigerator or in the freezer — the greater the loss of vitamin C in the milk. Other studies have shown that refrigeration beyond two days may reduce the bacteria-killing properties of breast milk and long-term freezer storage may lower the quality of breast milk's lipids. It's also important to note that breast milk expressed when a baby is a newborn won't as completely meet the same baby's needs when he or she is older.

Keep in mind that storage guidelines may differ for preterm, sick or hospitalized infants.

How do I thaw frozen breast milk?

Thaw the oldest milk first. Simply place the frozen container in the refrigerator the night before you intend to use it. You can also gently warm the milk by placing it under warm running water or in a bowl of warm water. Avoid letting the water touch the mouth of the container.

Never thaw frozen breast milk at room temperature, which enables bacteria to multiply in the milk. Also, don't heat a frozen bottle on the stove or in the microwave. These methods can create an uneven distribution of heat and destroy the milk's antibodies.

Use thawed breast milk within 24 hours. Discard any remaining milk. Don't refreeze thawed or partially thawed breast milk.

Thawed breast milk may smell different than freshly expressed milk or taste soapy due to the breakdown of milk fats, but it's still safe for your baby to drink. If your thawed breast milk smells rancid — due to enzyme activity during chilling — try scalding your freshly expressed milk so it bubbles around the edges but doesn't boil. Then quickly cool and freeze it. This will deactivate the enzyme.

What else do I need to know about breast milk storage?

During storage, expressed breast milk will separate — causing thick, white cream to rise to the top of the container. Before feeding your baby, gently swirl the contents of the container to ensure that the creamy portion of the milk is evenly distributed. Don't vigorously shake the container or stir the milk. Also be aware that the color of your breast milk may vary, depending on your diet.

Last Updated: 2009-12-01
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