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How to Store Breast Milk

Advice From a Lactation Consultant

For most infants, breast milk serves as the best source of nutrition and improvement for their general health, growth and development. It also decreases the risk for certain infections and diseases.

Ideally, your baby should have only breast milk for the first six months. Then, in addition to the introduction of solid foods, it is best to continue breastfeeding for up to 2 years.

Preparing and Expressing

As you prepare to and express breast milk for your baby, be sure to practice good hygiene, explains Northwestern Medicine Lactation Consultant Sara Pop, BSN, RN, CBC, IBCLC, RNC-MNN. A couple key practices include:

Hand expression is great to do for the first few days after delivery, Pop explains. Since this early milk is thicker, a pump might not be as effective.

The sooner you give milk you express, the better for your baby.
— Sara Pop, BSN, RN, CBC, IBCLC, RNC-MNN
If you opt for pumping at any point, you may want to start pumping a few weeks before you will be away from your baby or need it for other reason. This not only allows you to practice pumping, but it also gives you time to build up a reserve and to accustom your baby to bottle feeding.

Storing the Milk

No matter which method of expression you choose, Pop says there are important practices to keep in mind:

  • When you express milk, label it with the date and time. That way, in the future, it will be easier to use the oldest milk first when thawing out
  • Freeze milk in small quantities (2 to 4 ounces) so that not much is wasted between thaws. Breast milk expands as it freezes, so make sure there is extra space in the bag or container.

For proper storage time and temperature, the Centers for Disease Control and Prevention (CDC) has various guidelines, depending on the status of the milk.

Freshly expressed or pumped milk should be stored:

  • On a countertop at room temperature or lower for no more than four hours.
  • In a refrigerator for no more than four days.
  • In a freezer and used within six months, though 12 months is acceptable too.

Previously frozen, thawed milk should:

  • Be stored on a countertop at room temperature or lower for no more than two hours.
  • Be stored in a refrigerator for no more than 24 hours.
  • Never be refrozen after having been thawed.

“The easiest way to thaw milk is to leave it out overnight in the fridge or run it under warm water in the sink,” Pop says. “You can feed with cold or warm milk, but do not microwave the milk. That could make it too hot for the baby.”

If you have any leftover milk that the baby did not finish from its bottle, you can attempt another feeding with that milk within two hours after the baby initially finished feeding.

Additionally, there are facilities and programs, such as the milk lab in Northwestern Medicine Prentice Women’s Hospital, that help with breastfeeding and milk expression. At this milk lab, there are three full-time milk technicians who collect, prepare, store and distribute human breast milk to support the 86-bed NICU.

Whether clinician-assisted or done by yourself, providing expressed milk is often key for the health of your infant.

“The sooner you give milk you express, the better for your baby,” Pop explains. “If you express milk frequently, you can consistently have fresh milk to provide.”