Can i mix breast milk from 2 different pumping sessions

Most mothers protect their breast milk like it is liquid gold — for good reason. Because of this, many new moms have questions about milk storage, specifically combining milk from different pumping sessions or even different days. While the internet often provides conflicting information on topics like these, most experts tend to agree on what is and isn't allowed when it comes to mixing breast milk from different days.

What Is Wrong With Combining Breast Milk From Different Days?

Formula_and_breastmilkvia Wikimedia Commons/Jengod

Whether you're a working mom, a stay-at-home mom who is exclusively pumping, or a mom who alternates between breastfeeding and pumping, there may be times when the milk you pump from one session isn't quite enough for what your baby is currently consuming when bottle-fed. When this happens, you may want to combine breast milk from different days to fill it out.

However, the team at Verywell Family says you should be careful whenever you combine breast milk from different days because this can cause bacteria growth or other complications if not done properly.

For example, you should not combine freshly pumped breast milk with a previous day's supply that is already refrigerated. Doing this will warm back up the already chilled breast milk, which can cause the milk to expire faster or become contaminated with bacteria. Even if you think it will not matter, the repercussions of this will not be pleasant.

Similarly, adding freshly pumped breast milk into a batch of already-frozen milk will cause it to thaw. This will cause the milk to also expire, meaning it won't remain viable for long after you combine the two versions of milk. Once thawed, frozen breast milk is only viable for 24 hours. So instead of saving more milk, you're actually losing some of your supply through this practice.

How To Safely Mix Breast Milk From Different Pumping Sessions

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Although combining freshly expressed breast milk with already cooled milk in the fridge or freezer isn't recommended, there are ways to combine milk from different pumping sessions if needed. In fact, the Centers for Disease Control and Prevention (CDC) says there's an easy way to safely mix breast milk from different pumping sessions or even different days.

  • To begin, you must take the freshly expressed breast milk and cool it in the fridge or with ice packs for at least 30 minutes before combining it with other breast milk already in the fridge.
  • Once cooled, you can combine with other milk in the fridge, assuming it is not yet past its shelf life of 4 days — just make sure you do so in a safe, sanitary way that doesn't risk contamination.
  • Also, make sure you label the milk with the correct date for the oldest batch in the combination, as that milk won't magically gain extra shelf life just because you mixed newer breast milk in with it.

Similarly, you can also combine freshly expressed breast milk with milk that is already at room temperature, assuming you will use it all within 4 hours of when the older milk first adjusted to room temperature. However, you should not do this if you're wanting to refrigerate the milk you just pumped, as milk that has been warmed up cannot safely go back into the fridge a second time.

Finally, the Mayo Clinic never recommends combining breast milk into amounts that exceed what your child consumes in a single feeding. If you have more than that after you pump, consider splitting up the milk into smaller batches so none of it goes to waste.

Breast milk storage is anything but easy. However, getting these rules down will help keep your child happy and well-nourished without any tummy troubles down the line.

Sources: Verywell Family, Centers for Disease Control and Prevention, Mayo Clinic

Yes, it’s okay to combine breast milk from different pumping sessions, as long as you cool the milk to the same temperature before mixing them together. Label the container with the age of the oldest milk and store it accordingly. However, if you have a special needs or high-risk baby, it’s better to avoid combining containers of breast milk, since there is a risk of contamination when milk storage containers are repeatedly opened.

Can I mix breast milk from different pumping sessions?

Yes certainly you can combine breastmilk but there are a few guidelines.

If you are pumping twice in a day, keep the first milk covered in the fridge.  Then when you express again, you will need to use a different bottle and then chill that milk before adding it to the first milk.

You should not add your warm breast milk (at body temperature) to the chilled fridge milk.  You need to cool the warm breast milk before you add it to the already chilled milk.

If you are expressing over several days, we recommend that you freeze the milk in small quantities to avoid wasting it.

Just make sure you cool down your freshly expressed breastmilk before you add it to the frozen stored milk.

In other words, if you have 50mls pumped, cool it and then add to the frozen supply for the baby’s feed.  Only add cold milk to cold milk or cold milk to frozen milk.

Because you never want to waste breast milk, you might consider freezing it in relatively small amounts for each feed. This way, if your baby doesn’t take it all, you won’t be throwing it out, plus it will be quicker to defrost and warm.  Read our suggested How Much Does Baby Drink

If your baby does not drink all the milk in one feed – you CANNOT reuse the milk later, you will need to discard it.