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 for healthy infants:

• Room temperature. Freshly expressed breast milk can be kept at room temperature for up to six hours. However, it's optimal to use or properly store the breast milk within four hours, especially if the room is warm.
• Insulated cooler. Freshly expressed breast milk can be stored in an insulated cooler with ice packs for up to one day.
• Refrigerator. Freshly expressed breast milk can be stored in the back of the refrigerator for up to four days in clean conditions. However, it's optimal to use or freeze the milk within three days.
• Deep freezer. Freshly expressed breast milk can be stored in the back of a deep freezer for up to 12 months, but using the frozen milk within six months is optimal.

Keep in mind that 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.

It's also important to note that your breast milk changes to meet your baby's needs. Breast milk expressed when a baby is a newborn won't as completely meet the same baby's needs when he or she is a few months older. Also, storage guidelines might differ for preterm, sick or hospitalized infants.