Mom holding her baby and smiling.

There are millions of types of bacteria—some are good, some are bad. They’re microscopic and live on every surface. Bacteria can be found on your skin, in your car, on your food, and on every hard or soft surface in the world. While exposure to small amounts of harmful bacteria can help us build up a level of immunity, larger bacterial burdens lead to infections. Evading all of the bacteria in the world is impossible, but there are steps you can take to reduce the number of bacteria that you and your loved ones come in contact with. This is especially important in regard to breastfeeding and breast pumping. There are bacteria around your nipples and when you use a breast pump, there will be trace amounts of bacteria that get into the milk. However, utilizing the proper storage methods will keep bacteria levels low and keep your milk safe for your baby to consume. To help you get the most out of your breast milk storage, here’s a few guidelines on how long breast milk lasts.


The Basics: Breast Milk Storage Guidelines


Regardless of how you plan on storing your breast milk, it’s imperative that you take the proper steps ahead of time for the safest, most hygienic process. Before you do anything, wash your hands with soap and warm water for at least 20 seconds. Make sure that you get in between your fingers, the backs of your hands, and around your fingernails. If you can’t wash your hands, alcohol-based hand sanitizer will suffice. Next, you should prepare your breast pump according to the manufacturer’s instructions. Make sure that your breast pump has been thoroughly cleaned according to the CDC guidelines beforehand to avoid contaminating your breast milk.

How to Store Breast Milk After Pumping


One great tip for storing your breast milk after using a breast pump is to do so in smaller amounts so that you don’t waste any. It’s recommended to store your breast milk in 1 to 2-ounce portions and adjust once you get a better idea of how much your baby consumes during a feeding. Make sure that you leave a little space in the container to account for expansion during freezing and always clearly label the container with the date it was stored.

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Try to either refrigerate your breast milk or freeze it as soon as possible after you’ve pumped. If you’re not able to do this, such as in the case of working moms with limited accessibility to a refrigerator, use an insulated cooler that was designed for storing breast milk. This will help limit excess bacterial growth, thus keeping your breast milk safe for your baby. There are plenty of options for containers to store your breast milk, so find something that works for you.

The Best Storage Containers for Breast Milk


There are hundreds of different products online that are marketed for breast milk storage, but not all of them should be considered. The best way to ensure that your breast milk stays safe for consumption is to store it in covered glass or hard, BPA-free plastic containers. You can also use BPA-free bags, as long as they’re specifically made for breast milk storage—do not store your breast milk in Ziploc sandwich bags. If you’re using breast milk storage bags, consider placing them inside of a hard container in your refrigerator or freezer to avoid leaks or tears.

Another popular option emerging among new mothers is storing breast milk in silicone molds. These molds are similar to ice cube trays and provide mothers with options for easier thawing of small quantities of breast milk. Make sure that you utilize silicone molds that are created for breast milk storage for safety reasons.

Risks of Improperly Stored Breast Milk


Breast milk contains a level of antibacterial and immune properties that help prevent bacterial growth in milk for a limited amount of time. It’s no surprise, therefore, that the longer you leave breast milk improperly stored, the more bacteria will be present. Since bacteria thrive in warm temperatures, the time requirements for safe storage decreases depending on the environment. This is why you need to use room temperature breast milk far sooner than breast milk that has been properly frozen. If you improperly store breast milk, you’ll lose essential nutrients and increase the risk of bacterial contamination. This can lead to dangerous, life-threatening infections depending on the number of bacteria that’s present. If you think that your breast milk has been contaminated, throw it out.


CDC Recommendations for Safely Storing Breast Milk


How you store breast milk depends on whether you’re going to keep it at room temperature, in the refrigerator, or in the freezer. You also have to take into consideration whether the breast milk is freshly expressed, thawed after being previously frozen, or leftover from a feeding. According to the CDC recommendations, each situation requires different guidelines, which are listed as follows:


  • Freshly Expressed at Room Temperature: breast milk lasts up to four hours
  • Freshly Expressed in the Refrigerator: breast milk lasts up to four days
  • Freshly Expressed and Frozen: breast milk lasts up to 12 months, but it’s best to use within six months
  • Thawed, Previously Frozen at Room Temperature: breast milk lasts between one and two hours
  • Thawed, Previously Frozen in the Refrigerator: breast milk lasts up to 24 hours


Any breast milk that you have frozen and thawed should never be refrozen. Doing so is dangerous to your baby’s health. If you thaw milk and it’s not used within the appropriate amount of time, it should be thrown away. Additionally, any breast milk that’s leftover from a feeding should be used within two hours after your baby has finished feeding, regardless of how it was stored.


If your baby was born premature or has certain health-related issues, these guidelines change. When your baby is at a higher risk for infection, it may be dangerous to feed them breast milk that’s been left at room temperature. To ensure that bacteria levels are low, you should use breast milk within one hour of pumping or put it into the refrigerator immediately. These guidelines can change depending on your baby’s condition, so it’s always best to discuss any concerns with your pediatrician.


Tips for Storing Breast Milk at Room Temperature


Storing breast milk at room temperature needs to be done in a specific way to reduce bacterial growth. Always keep your breast milk away from heat sources, as higher temperatures speed up bacterial growth. While preparing your breast milk for proper storage, place a cold towel over the container to help keep temperatures down. You should then secure the breast milk in whatever container that you’re going to use for storage. Make sure that it’s intended for storing breast milk for safety reasons. If the environment is 77° F or higher, do not let your breast milk sit out. This is too high to be considered a safe room temperature.


How to Thaw Breast Milk Safely


The process of thawing your breast milk is just as important as how you store it. There are specific guidelines on safe thawing practices. Never thaw your breast milk at room temperature. This can increase bacterial growth and therefore, increase the risk of infection to your baby.


You should also avoid thawing your breast milk in the microwave. Doing so can lead to hot spots within your breast milk that can burn your baby’s mouth and throat while destroying the nutrients in the milk itself.


The best way to thaw your breast milk safely is to gradually let it thaw in the refrigerator. This will reduce bacterial growth and ensure that your breast milk stays safe for consumption. If that’s not possible, using lukewarm water is the next best option. You can also hold it under the tap of lukewarm water. If you have any questions regarding the best way to thaw breast milk safely, talk to your doctor.


Breast pumping is an excellent way to supplement nursing, but it’s important that you take the proper steps when storing your breast milk. When you’re done using your breast pump and putting your breast milk away, follow the CDC guidelines to properly clean your breast pump parts and avoid any contamination. When choosing your breast pump, take your time and do your research. Remember that the Affordable Care Act requires that your insurance provider covers breast pumps, breastfeeding support, and other supplies that you may need. Byram Healthcare is here to help you find the perfect breast pump through your insurance coverage.