Milk Storage

If you ever wonder whether you need to discard your milk, or have other questions about lactation or breastfeeding, please contact us first at the Lactation Study Center (585-275-0088 or lsc@urmc.rochester.edu)

Recommendations for Breast Milk Storage

There are different recommendations for how long to store expressed breastmilk. This is because we don’t want parents to throw away important breastmilk, but we also want to make sure babies don’t get sick because milk was stored improperly. While the CDC recommends shorter times for milk storage, other experts, like those at the Academy of Breastfeeding Medicine, consider stored breastmilk safe for longer. After weighing all the evidence and the recommendations, this is what we believe will help you keep your milk safe for use with baby:

Research Shows Milk is Safe Longer

• Human milk is safe after expression for a range of times, based on the temperature of storage, the cleanliness of storage containers and the way it is thawed. Human milk has many antimicrobial factors in it that prevent the growth of harmful bacteria or spoilage, like lactoferrin, lysozymes and immunoglobulins.
• Research has shown that these properties decrease after 4 days of refrigerated storage. However, research has not shown that these properties are gone by 4 days. Research also does not find that bacteria start to grow in the milk at 4 days.
• There are very few instances of babies becoming sick after ingesting contaminated breast milk, and they are in premature babies. Also, the milk containers and cleaning areas were implicated in these cases, not the timing of milk storage. 
• If you are storing milk in your freezer and the freezer loses power keep the door closed as much as possible. This will keep the food inside safe for 24-48 hours. Milk that is still frozen or “slushy” can be re-frozen. Milk that is thawed but still cold should be used based on refrigeration guidelines, or discarded. Warm milk should be discarded.

Pumping and Storing Milk

• Before you pump, we recommend you wash your hands, make sure your pump parts are clean and dry, and pump into clean bottles or bags. If you are pumping in a shared location, or with a hospital-grade shared pump, consider wiping them down with cleaner and a towel before and after use.
• After pumping, label and date your milk. Store in clean bottles or bags that are approved for breast milk. Other plastic bags, or bottles with the recycle symbol number 7, may contain BPA or other plastics that could get into your milk.
• Get your milk into the refrigerator or freezer as soon as possible after you pump.

Cleaning and Maintaining Your Pump

• Pump parts should be completely disassembled and scrubbed inside and out in hot, soapy water after use. Rinse in hot water, then allow to air dry. If you are not able to air dry, then consider sterilizing the parts, then shake them, and wipe with a dry ,fresh, clean towel or paper towel.
• There is no evidence that sterilization of pump parts is necessary, provided breast pump parts are scrubbed in hot soapy water and allowed to air dry after use.
• As long as you are cleaning pump parts at least once a day, it is safe to store pump parts in the refrigerator between sessions as long as they are stored in a clean storage bag or container.

Milk Management

• Frozen milk should be thawed in the refrigerator overnight, or in lukewarm water. This process takes time and breastfed babies are not always patient, so plan ahead! Bags stored and frozen flat will thaw faster than bottles or bags frozen upright. Check those zippers to make sure they are closed!
• It may be safest to use thawed milk within 24 hours of thawing, though we don’t have good research in this area. Based on the best available evidence, it appears thawed milk should be used within 4 hours after heating.
• Babies should be fed fresh milk first. It has the most immune properties and benefits. If fresh milk isn’t available, many people recommend using the oldest frozen milk you have, so that you limit your overall storage time.
• It is still most safe to only heat up and feed the milk you think your baby will take, even if this means heating up more than one smaller bottles. If you are using infant formula, or mixing your breast milk with formula, the milk should be discarded within 1 hour of being fed to a baby.
• You can avoid discarding breast milk by storing it in quantities slightly smaller than your baby takes. Freezing milk in larger than 4oz bottles or bags may mean you have to waste unused milk. You may also want to store some 2 oz bottles or bags for small “snack,” additions to a larger feed, or mixing with baby food.

Milk Management for Premature Babies

• We recommend you wash your hands, make sure your pump parts are clean and dry, and pump into clean bottles or bags. If you are pumping in a shared location, or with a hospital-grade shared pump, consider wiping them down with cleaner and a towel before and after use.
• After pumping, label and date your milk. Store in clean bottles or bags that are approved for breast milk. Other plastic bags, or bottles with the recycle symbol number 7, may contain BPA or other plastics that could get into your milk. Many NICUs will provide sterile bottles that work best for their storage and thawing facilities.
• We recommend following your NICUs guidelines for milk storage as there is an increased risk of contamination with transportation and adding fortifiers to milk. If there is milk you can’t use in the NICU that is still within safe range based on our recommendations, you could store it for use when your baby is older and healthy. We do not recommend storage pump parts in the refrigerator before pumping sessions.
• Put your milk on ice in a cooler or insulated bag to transport to your baby’s bedside. This will keep the milk safe for longer.