Q. How long does expressed milk keep?
A. Refrigerated breast milk, which can be stored in glass, plastic, or stainless steel containers, is best used within 48 hours. Frozen milk keeps for three months if your freezer has a separate door, two weeks if it doesn't. Freeze expressed milk in glass or plastic containers, or in bags designed for freezer storage, and thaw it by running the container under cool, then warm water until it's at room temperature. Keep milk refrigerated until you're ready to use it. If your baby doesn't consume it within 48 hours, throw it out: You should never refreeze breast milk.
What about nutrient loss during storage? Though expressed milk loses a few vitamins and minerals, the amounts are so small there's no need to be concerned, says Jay Gordon, M.D., a pediatrician who advises La Leche League, in Santa Monica, CA.