How Long Can Breast Milk Stay Out?

Whether this is your first time nursing or your fourth, you probably have many questions. From “how should I store breast milk” to “is it safe for baby to finish milk from a previously consumed bottle,” inquiries abound. But one of the most common questions new (and expectant) parents ask is “how long can breast milk stay out, i.e. is it safe for breast milk to be stored at room temperature?”

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Here, we catch up with some breastfeeding experts to answer parents' most pressing questions about leaving breast milk out.

Can Breast Milk Be Stored at Room Temperature?

So what's the deal with leaving breast milk out at room temperature? Is it truly safe for your baby? The answer is yes, says Jessica Madden, MD, IBCLC, pediatrician, neonatologist, lactation consultant, and the medical director ofAeroflow Breastpumps. “Pumped breast milk can be left out at room temperature for a period of time prior to being consumed or refrigerated,” she explains.

There are a few caveats, though. First of all, you need to make sure that you are using a proper container for storage. "Breast milk should always be stored in containers that have been thoroughly cleaned with warm, soapy water, and dried prior to use," Dr. Madden says. Storage containers can be made of either glass or plastic. "At the present time, one type of storage container is not recommended over the other," she says.

And what exactly does “room temperature” mean? Room temperature generally means 77 degrees Fahrenheit, and that's the temperature that the Centers for Disease Control and Prevention (CDC) points to when they discuss storing breast milk at room temperature. The Academy of Breastfeeding Medicine (ABM) notes that for the purposes of safely storing breast milk, room temperature can be anywhere between50 to 85 degrees Fahrenheit.

As Jenelle Ferry, M.D., neonatologist and director of feeding, nutrition and infant development at Pediatrix Neonatology of Florida, reminds, the temperature in your home can vary, based on location, so that's something to keep in mind when leaving breast milk out. "Be careful not to store room temperature breast milk next to a window that may allow sunlight to create a warmer environment," Dr. Ferry advises.

How Long Can Breast Milk Stay Out?

The CDC advises that breast milk can stay out on the counter at room temperature (77 degrees F) for four hours.The ABM says that there may be a bit of variation in terms of how long breast milk can stay out, but it depends on the circumstances. Breast milk can stay out for about four hours in temperatures between about 80 to 89 degrees F. But if room temperature is lower, for example, and the milk is kept in a very clean container, six to eight hours may be safe as well.

What Happens If You Leave Breast Milk Out for 4 Hours—or More?

Most parents err on the side of caution and go with the four hour CDC rule. Dr. Madden says that how long to leave milk out also depends on the health of your baby. "I typically recommend that breast milk be tossed out if it's been at room temperature for more than six to eight hours, and to only give breast milk that's been out for between four to eight hours to healthy, full-term babies," she says. "This is because premature infants are at a higher risk of infection due to having immature immune systems."

However many hours your milk has been left out, Dr. Madden says that a little common sense goes a long way. "Breast milk should be thrown out if it smells or tastes like it is spoiled, no matter how long it's been at room temperature," she says.

Dr. Ferry agrees with this sentiment. “If milk smells sour, it has gone bad and should definitely be dumped,” she says. “One of the risks of breastmilk left out too long is growth of bacteria, which can't be detected on visual inspection.” There isn't a specific appearance, for example, or color of milk that denotes it's “bad.” But milk that's left out too long can result in vomiting or diarrhea in your baby, Dr. Ferry adds.

Leslie Owens, RN, IBCLC atMother Nurture Maternity, recommends staying within the four hour range when it comes to how long to leave milk out, because of the risk of bacterial contamination. “If you truly want to avoid wasting milk that was left out, you can also store and save it to use in baby's bath water as a milk bath,” she recommends. “Many believe that breast milk has many benefits for the skin.”

What If Your Baby Doesn't Finish Their Bottle?

One question that Dr. Madden gets frequently is what to do with room temperature breast milk that's left over in a bottle after a feeding. To answer this question, Dr. Madden refers to the ABM protocol for milk storage, which recommends tossing any remaining milk that has been at room temperature for more than one to two hours. "Leftover milk should also never be given to a premature infant due to their higher risk of developing infections," she advises.

How Can You Safely Store Breast Milk?

Besides questions about how long you can leave milk out, parents often have many questions about how to store milk in the fridge and freezer. You can refer toCDC guidelinesfor the basics about safe milk storage but, in a nutshell, freshly pumped breast milk can be stored in the fridge for about four days, and it can be stored in the freezer for between six to 12 months. After you've taken your milk out of the freezer and defrosted it, you can leave it out for one to two hours and you can leave it in the fridge for about 24 hours. Unfortunately, you can't refreeze thawed milk.

Other milk storage tips for experts? Owens recommends not storing too much milk at once so your precious pumped milk doesn't go to waste. "Parents also often ask what quantities they should store milk in and I typically advise them to store in one to two ounce increments in the beginning and eventually three to four ounce increments as your baby gets older," she says. When freezing milk, Owens recommends using milk storage bags, and labeling each bag with the date. "Order the milk from oldest milk at the front to the freshest milk at the back so it will not be forgotten before it expires," she says.

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Pumping and storing breast milk is a huge job, so kudos to all the parents out there who are doing it. It's common to have tons of questions as you go along—we've all been there! Never hesitate to reach out to a pediatrician or lactation consultant if you have further questions—big or small—about handling pumped milk.