Topic Overview

Because what is in your breast milk changes as your baby develops, it is best to use milk as soon as possible after pumping or expressing it. Also, the antioxidant and other protective properties are most important and beneficial to your baby when breast milk is fresh. The protective components of breast milk decrease with refrigeration and freezing.¹ But stored breast milk is the next best thing to fresh breast milk as a complete and nutritious food source for your baby. Stored breast milk is still better for your baby than formula.

Breast milk can be stored and then used in the following ways:²

• Kept at room temperature [60°F (16°C)] to [85°F (29°C)] for 3 to 4 hours. If the milk was collected under clean conditions, such as properly washed hands and properly cleaned pump parts and containers, milk may be kept at room temperature for 6 to 8 hours.
• Kept fresh in a cooler with blue ice [59°F (15°C)] for 24 hours
• Stored fresh in the refrigerator [39°F (4°C)] for up to 72 hours. If the milk was collected under clean conditions, it may be stored for 5 to 8 days.
• Kept in a refrigerator freezer [4°F (-15.6°C)] for up to 6 months

Safe storage tips

Follow these tips when you prepare breast milk for storage.

• Be sure to wash your hands before pumping or handling milk that will be stored.
• Storage containers should be clean and dry. They do not need to be sterile. Wash them in hot soapy water or in the dishwasher.
• Plastic bottle liners or small ziplock bags can be used for storage, held upright in cups. Be sure the bags are sturdy and stored in a place where they will not get punctured or damaged.
• If you plan to freeze the milk, allow a little space at the top of the bag—the milk will expand when it freezes. It's also important to put the date the milk was pumped on the outside of the bag. The date will help you know which milk to use first and when to get rid of milk you didn't use.
• Milk from both breasts expressed during the same session can be combined in one container. It is best to use a container that holds enough milk for one feeding. You are less likely to have to discard unused milk.
• For the most consistent temperature control, store milk at the back of the refrigerator or freezer compartment.
• When thawing or warming breast milk, run warm water over the storage container (which may be a bottle or a plastic bag) until the milk becomes slushy. You can then heat the container gently in a pot of warm water on the stove until the milk is slightly warm to the touch.
• Frozen breast milk will separate because the fat floats to the top. This separation is normal and does not mean that the milk has spoiled or is otherwise unusable. After thawing breast milk, shake the container gently and the fat will redistribute evenly.

Do not:

• Refreeze thawed milk.
• Use thawed (and then refrigerated) breast milk after 24 hours.
• Use a microwave oven for warming milk. Microwaves heat unevenly, creating hot spots that can burn your baby's mouth and throat.

There is very little research about how safe it is to refrigerate and reuse breast milk left over from a previous feeding. But many experts say it is best to throw away any breast milk left in the bottle after a feeding.