How to defrost breast milk?

To freezing breast milk, you can use a breast milk storage bag food-grade silicone that is BPA-free (Bisphenol A). You can also opt for tinted glass containers, such as jam jars, and if you use plastic bags, make sure they are BPA-free. We recommend writing the expression date on each container to keep track, and freezing the milk as soon as possible after expressing. 

It is best to store milk in small quantities (less than 120 ml, or the equivalent of one bottle feed), so you keep the minimum amount needed to limit waste and use exactly the quantity required.

There is no universal freezing date — it depends on the method used. 

In a freezer at between -18 and -20°C, breast milk can be kept for between 4 and 9 months, depending on the hygiene precautions taken during collection. The recommendations of the French Food Safety Agency (AFSSA) are not to keep frozen milk for more than 4 months in the freezer for hygiene reasons. 

In the three-star compartment of a fridge-freezer, it can be kept for between 2 and 3 months. 

In the freezer compartment of a fridge, breast milk can be frozen for a maximum of two weeks. 

To find out more on the subject, have a look at our article on breast milk storage. 

Thawed breast milk must never be refrozen ! 

Every parent will find the method that best suits their habits and needs.

Defrosting breast milk in the fridge

If you have stored breast milk in the freezer and wish to use it but are not in a hurry, you can simply place it in the fridge the evening before you need it. 

Allow around 8 hours for a complete defrost before giving the refrigerated milk to your baby.

Make sure your milk is fully defrosted before warming it. Once ready, you can warm it under warm/hot running water from the tap for a few minutes.

Refrigerated breast milk often separates into two layers: a "fatty" layer that floats to the top, and a "watery" layer. This separation of the milk is completely normal after a period of storage. You can gently mix the milk by making circular movements with the container.

Please note: never refreeze defrosted breast milk. Equally, do not reheat breast milk that has already been warmed more than once.

Defrosting breast milk with warm water

If you are in a bit of a rush and cannot wait 8 hours for it to defrost (because your baby is hungry – we've all been there!), don't panic. You can run the container under the tap to defrost the breast milk gradually. Start with cold water so as not to cause a sudden temperature change, then gradually increase the temperature.

Once your milk is warm, gently swirl the bottle so that the heat is evenly distributed throughout the milk.

Defrosting breast milk in a bain-marie

Take a small saucepan and fill it halfway with water. Heat it without ever letting it boil. If it has reached boiling point, wait for the temperature to come back down.

Remove the saucepan from the heat to avoid overheating the breast milk and to prevent any risk of scalding…

Once you have removed the saucepan from the heat, you can place the bottle directly in the water. Allow a few minutes if the milk is coming from the fridge, and around ten minutes if it is frozen. Gently but regularly swirl the container to avoid hot spots.

Defrosting breast milk with a bottle warmer

Another option for defrosting breast milk is to place it in a bottle warmer. There are many types available, operating either on a bain-marie principle or a steam principle.

Do of course read the instructions specific to your model, but here are a few tips that may help you:

– Change the water with each use, particularly if your device works by steam.

– Heating time is proportional to the amount of milk present. You can cut out the heating time chart to always have it to hand.

In all cases, once warmed, remember to gently swirl the container so that the heat is evenly distributed throughout the milk.

And most importantly, always place a drop of milk on the inside of your wrist to make sure it is at the right temperature before giving it to your baby.

Can I use a microwave? 

The answer is no! Parents should never put breast milk in a microwave. This method destroys some of the nutrients present, resulting in a loss of health benefits for babies. In addition, significant temperature differences can be found within the same bottle of milk warmed this way, which can create safety issues. The container may not feel hot, but the milk can be scalding in places at the centre.

Thawed breast milk keeps for a maximum of 24 hours in the fridge, and 1 hour at room temperature, as this is an environment conducive to bacterial growth. If the child has already drunk from the cup or container, they may have transferred bacteria from their mouth into the milk, thereby contaminating it. It is therefore best to discard it in that case. 

Store only small volumes of breast milk (less than 120 ml). This will allow you to warm them more quickly and avoid wasting your milk if your baby does not consume it all at once.

If, when thawing, you notice that your milk has a strange smell — like "rancid" or soapy — do not worry, it can still be consumed (provided it has been correctly frozen). Some mothers' milk can contain a lot of lipase, which causes these unpleasant odours that some babies may reject. However, there is a way to prevent this. 

Warming breast milk is quite straightforward, provided you follow the appropriate methods and recommendations to preserve its unique qualities and avoid the risk of burns to your baby.

Please make sure that your loved ones or those caring for your baby during the day are familiar with these methods, as well as the different ways to store breast milk.

Happy breastfeeding!