April 14, 2024
Close this search box.
Close this search box.
April 14, 2024
Close this search box.

Linking Northern and Central NJ, Bronx, Manhattan, Westchester and CT

This Won’t Hurt a Bit and Other Pediatric Myths Debunked

Q: Sadly, my maternity leave will be coming to an end and I plan to pump and store my breastmilk. How long can I store my breastmilk in the refrigerator and freezer? How long can formula be used once the bottle has been opened?

A: Before we discuss timing, I just want to say a few brief words about storage. As many of you already know, pumping (especially at work) is not easy. It takes time and commitment so please make sure expressed breast milk is stored properly so it does not (God forbid) have to be discarded. Make sure you store it in a clean, hard container—glass or plastic (make sure it is BPA free). Bags are convenient but risky as they can easily tear and leak, which may also cause your eyes to leak as you cry in frustration. Since there is already enough stress and often tears when you first go back to work, it is best to avoid storing in plastic bags alone. If you can’t resist the clean-up advantage they offer then opt for special breast milk storage bags, but please put them inside a harder container before freezing.

1. Timing

Room Temperature: Breast milk can be left out at room temperature for up to 4–6 hours but please try to keep it closer to 4.

Refrigerator: 3–5 days but 3 days is preferred

Freezer: 6–12 months (6 months preferable)

Coolers with ice packs come in handy at work and milk can be safely stored in them for a day.

My esteemed and very smart colleague Dr. Kim Kinney came up with an easy way to remember this when you don’t have this article (or a smart phone) handy. Just remember 4, 5, 6 as the temperature gets progressively colder:

Room temp: 4 hours

Fridge: 5 hours

Freezer: 6 months

2. Warming the Milk

It is best to plan ahead by putting frozen breastmilk in the fridge the night before the day you plan to use it. To warm it, put the container under warm running water or submerge it in a bowl of warm water.

Despite the fact that we are all always in a rush, do not heat the container in the microwave. This creates uneven heating with some pockets that are very hot and others that are cold. You could potentially burn the baby’s mouth. Also, some studies have shown that rapid heating might affect the antibodies in the milk.

3. A Few More Tips

If you write the date that you pumped on the container, you will not spend time worrying about how long the milk has been in the fridge or freezer (and we all have enough to worry about).

Both the fridge and freezer are coldest towards the back wall and this is the best place to keep your bottles.

Remind your babysitter to use the oldest containers of stored milk first. The milk that you express when your baby is a newborn will not completely meet the needs required by the baby when he or she is a little older.

Don’t fill containers to the top as breast milk expands when freezing.

Don’t be surprised if your thawed breastmilk smells different from fresh breastmilk. It does not mean that it’s spoiled. It just has a different odor and consistency. It’s completely fine to give it to your baby. If your baby is also unhappy about the new smell and actually refuses to drink it, you can try freezing the milk for a shorter period of time to see if that helps. If you and your baby cannot work it out please don’t panic—there is always…


One of the great debates of motherhood is whether to give your baby breastmilk or formula. Here is the very simple answer. Either one is fine. You are not a bad mother if you don’t breastfeed. We all know there are many, many benefits to breastfeeding (and this article is about storage, not about the debate of breast vs. formula) but if you are a new mom and you are having difficulty breastfeeding or coordinating your pumping at work, please don’t stress if you need to give your baby formula.

There are several options when it comes to formula:

1. Powdered—you just need to add water. Please make sure to read the directions carefully so that you use the appropriate number of scoops with the correct number of ounces of water.

2. Concentrated liquid—you also need to add water. Again, please read the directions carefully so you do not dilute it too much or leave it too concentrated.

3. Ready-to-feed—no need to add water; just pour into a bottle and you are good to go.

While ready-to-feed is the easiest, it is also the most expensive. It’s fine to use all three; just make sure you are mixing the powdered and concentrated formula correctly. Diluting formula with more than the recommended amount of water (thereby increasing the amount of water and decreasing the amount of formula per bottle) decreases the amount of calories and nutrients, which can slow physical growth and cause developmental delays. Excess water can also cause water intoxication, which can lead to electrolyte imbalance and seizures. Using less water and more powder or concentrated formula per bottle can actually lead to dehydration. Every bottle or can of formula has very specific instructions on preparation. Once the formula is opened and prepared, you can refrigerate most for up to 48 hours, but please check your bottles and cans since there are some that recommend use within 24 hours.

Remember your pediatrician is there to guide you along the way, so don’t hesitate to ask if you have any questions at all about breastmilk or formula. Feeding a newborn is not always as easy as it looks and not every baby will react the same way to the same option. There is no one-size-fits-all choice. What works for one Mom may not be great for another. As the brilliant Dr. Kinney has told many of her patients, “Breast is best but a happy Mom is better.”

By Nina Epstein

Nina Epstein is a pediatrician at Metropolitan Pediatrics in Teaneck whose three teenage daughters were raised on formula. They turned out fine… (aside from the usual teen girl drama, which breastfeeding cannot help you avoid. Sorry Moms.)

Leave a Comment

Most Popular Articles