Handling breast milk can be scary. Sometimes, it almost feels like dealing with dangerous stuff, and it seems that handling breast milk can be extremely complicated. But at the end of the day, it should be no more scary than handling any other food. To do so, you simply have to follow a series of rules that guarantee the greatest possible safety, and for breastmilk, it is no different.

Let’s take a look at the most common questions on this subject:

In what part of the fridge or freezer should I store breastmilk?

In what part of the fridge or freezer should I store breastmilk?
Always store breastmilk in the coolest part of the fridge or freezer, and avoid putting it in the door of the fridge. And try to reserve a section in the freezer exclusively for storing breastmilk to avoid transferring odors from other foods to the milk.

How long does fresh breastmilk last in the fridge?

Fresh breastmilk can be stored for about 5 days at a temperature of 0 to 4°Celcius (32 to 40°Fahrenheit). If the temperature is lower and the milk has been stored hygienically, it may also last up to 8 days.

How long does frozen breastmilk last?

You can store breastmilk in the freezer for about 6 months. In some freezers where the temperature is below -20°C (-4°F), it can last a few more months.

I have heard of other recommendations that are much more restrictive; why is there such a difference?

Unfortunately, storage recommendations for breastmilk can vary a lot. And in general, recommendations coming from the American Academy of Pediatrics or milk banks in South America are more restrictive.

What about at room temperature?

It depends on the room temperature. For reference, if breastmilk is below 24ºC, it is better not to keep it for more than 4 hours without putting it in the fridge. The higher the temperature, the less time it will be safe to keep it out. So, whenever you can, put breastmilk into the fridge to ensure that it stays fresh for as long as possible.

How can I tell if the milk has gone bad?

When breastmilk goes bad, it smells very bad. But this is very different from the slightly sour smell it can acquire due to lipase. See below for information and read here on how to avoid lipase fat degradation.

Can I reheat breastmilk?

No. Once breastmilk has been reheated, it is better not to repeat this process. Every time you heat the milk, this promotes the growth of certain bacteria that are potentially harmful and can be in the milk because of an unhygienic extraction or also because of cross-contamination: for example, caused by remains of milk in the breast pump or on surfaces on which the parts of the pump have been placed.

What if the baby doesn’t want the reheated milk?

Previously frozen and then reheated leftover milk that the baby has not wanted can be stored for up to 30 minutes after the feed. But this milk cannot be reheated and reused afterward. If your baby does not have it, the remaining milk needs to be disposed of.

What about the milk that the baby has not finished?

When the baby does not finish the milk, this has to be thrown away, as it has been in contact with the baby’s saliva and bacteria. It can be offered at a maximum of half an hour but cannot be reheated.

How can I defrost breastmilk?

To defrost breastmilk, it is always best to do this as quickly as possible. Previously, it was recommended to leave breastmilk thawing in the fridge for a few hours. However, now we know that the best way to prevent milk from losing its properties is to defrost one bit at a time, just before it is needed.

How do you defrost breastmilk? Here are four ways to do this:

• Heat water in a saucepan. When it boils, turn off the heat and place the container with the breastmilk inside. As an alternative to this method, you can heat water in a plastic container in the microwave. Take it out and place your breastmilk bag or container inside.
• Fill a container with hot water from the tap, place the frozen breastmilk in its bag or container in it, and let it defrost. If the water gets too cold, repeat the process.
• If you have a bottle warmer, you can also use it to defrost/heat up stored breastmilk.
• Try to freeze milk in small amounts, under 100ml/3.3 ounces, as this will make it much easier to defrost it easily.
• Don’t defrost breast milk directly in the microwave or on the stove.

What if I let breastmilk defrost in the fridge?

Frozen milk can be left to defrost in the fridge for up to 24 hours. But after that time, if it has not been used, it should be thrown away.

Even so, it is best to defrost breastmilk just before offering it to the baby and not to leave it thawing in the fridge. Remember that defrosted breastmilk cannot be frozen again once it has been thawed.

Can I use a microwave?

First of all, make sure that the containers you are going to put into the microwave are microwave safe. Although there is a lot of controversy about the use of microwaves for heating or thawing breast milk, here is some information so you can decide for yourself what you prefer to do:

• The biggest danger when using a microwave is the burns it can cause to the baby if the milk is not mixed enough before it is given to the baby.
• Secondly, milk can boil over, which could cause all the living cells in breastmilk to disappear.

However, if you want to use the microwave to warm or defrost breastmilk, keep the following in mind:

• Don’t overheat the milk (keep in mind that the natural temperature milk comes out of the breast is the body temperature).
• You have to mix the milk thoroughly before giving it to the baby, making sure that the temperature is uniform.
• Always prevent the milk from boiling.

Then the baby can safely have milk that has been heated or defrosted in the microwave. Even if the milk has inadvertently boiled in an isolated incidence and all the living cells die, this milk will still retain many nutritional properties. If this happens in one occasional feed, it will lose importance if the baby has otherwise been breastfed throughout the day.

Can I mix fresh breastmilk with breastmilk in the fridge?

You can do so when both are at the same temperature. But it is best not to mix refrigerated milk with freshly expressed milk to avoid bacterial growth. It’s best to only wait a maximum of one hour, depending on the quantity, when mixing them.

Can I wait before freezing breastmilk?

If you have breastmilk in the fridge and you know you will not use it within two or three days, it is best to freeze it. Freezing expressed milk expressed within 24 hours is ideal. You should always label it and freeze it for optimal storage.

My breastmilk smells sour

Breast milk contains lipase. Lipase is an enzyme that helps the baby by breaking down the fat in breastmilk and making it more digestible. But when the fat in breast milk degrades, it acquires a distinct rancid taste. This taste does not mean that the milk is bad or cannot be consumed, and, in fact, there are babies who accept it without problems. But some babies reject it, and, in this case, it can be warmed up to inactivate the lipase in breastmilk. You can find more information about this here.

How can I go out and about with my expressed breastmilk and warm the milk?

To go out, bring your expressed milk, hot water in a thermos flask, and a container if the place where you are going is not going to be able to provide this for you.

If it is going to take a long time before this milk is given to the baby, or it is very hot, it is better to take it out frozen. If it is not very hot or you are going to give it to the baby soon, you can bring it at room temperature.

When the baby shows signs of hunger, put the hot water in the container and place the milk bottle inside. Then, in a few minutes, it will be ready to be offered to the baby.