Guide: Freezing and storing breast milk safely

Dear Mom,

It is wonderful that you want to give your baby breast milk! Sometimes, however, direct breastfeeding is not possible – for example, when you return to work, exercise, or simply want to catch up on sleep while your partner takes over feeding. This is where pumped breast milk comes in! It is a great alternative and continues to offer your baby many health benefits.

To ensure your precious breast milk remains safe and in good condition, there are a few simple rules for storage.

When is the best time to pump for storage?

Many midwives recommend not pumping milk for freezing during the first two weeks after birth. There are two good reasons for this:

• You and your baby need time to find your own breastfeeding rhythm.
• During this time, your body is adjusting to your baby's needs. Breast milk is constantly changing to provide exactly the nutrients your baby needs at that moment (from colostrum to transitional milk to mature milk). Older, frozen milk may no longer perfectly meet your baby's current nutritional requirements.

Choosing the right containers

The right containers are important for storing your pumped milk:

• Special breast milk bags: These are particularly hygienic, often pre-sterilized, and feature a practical scale and a space for noting the date. Some can even be attached directly to the breast pump. They also save space in the freezer. Medela, for example, offers special breast milk bottles and bags that make collecting and storing safe and easy. Medela's Easy Pour breast milk bags are ideal for freezing and easy to label.
• BPA-free breast milk bottles: Ensure they are made from BPA-free materials.
• Glass jars with screw lids: An eco-friendly choice! Make sure the jars are cold-resistant so they do not crack in the freezer. You can clean them easily (wash with dish soap and hot water, then let air dry).
• Avoid: Standard freezer bags or ice cube trays are not ideal, as they may contain plasticizers or fail to protect the milk sufficiently from germs.
• Standard & Safety: Look for products that comply with DIN EN 14350 (2023) for drinking equipment; this standard ensures that the materials, design, and labeling of baby bottles & bags are safety-tested.
• EU regulation on the BPA ban: Bisphenol-A has been banned in baby bottles across the EU since 2011; approved materials include polypropylene (PP), polyethylene (PE), and PET, which can be identified by recycling codes 01, 02, or 05.

Tip: Transparent containers or those that are easy to label are very practical

Preparing breast milk for freezing

• Hands and environment: Always start with clean hands and a clean work surface.
• Pre-cooling: Expressed milk is at body temperature. Therefore, always let it cool in the refrigerator firstbefore placing it in the freezer.
• Do not mix: Never add body-warm, freshly expressed milk to milk that has already been chilled or frozen. If you want to mix different portions, cool them separately first and then mix them.
• Filling portions: Only fill the containers to three-quarters, as milk expands when frozen. Small portions (e.g., 60-120 ml) are ideal to avoid waste. You can also mix several thawed portions later if needed.
• Labeling: Very important: Write the pumping date and the amount on each container. This helps you keep track of your "milk bank" and allows you to use the oldest milk first.
• Storage: Keep lids & seals separately in the refrigerator until the milk is added – this prevents condensation and bacterial growth.

Storing breast milk correctly

The shelf life of breast milk depends on where you store it. Here are the general guidelines for healthy, full-term babies:

• At room temperature (16-25 °C): Ideally a maximum of four hours. Under very hygienic conditions, up to six hours. In summer, at temperatures above 22°C, only a few hours.
• In the refrigerator (4 °C or colder): Ideally a maximum of three days. Under very hygienic conditions, up to five days. Some sources also mention up to four days at 0-4°C. Place the milk in the coldest part of the refrigerator immediately after pumping, ideally at the very back above the vegetable drawer. Do not store in the refrigerator door, as the temperature fluctuates there.
• In the freezer (-18 °C or colder): Ideally for a maximum of six months. Under very hygienic conditions, up to nine months. Some experts consider the quality acceptable even after another six months. Place the milk at the very back of the freezer, where the temperature is most constant. Ensure that containers in self-defrosting freezers do not touch the walls.
  • Important note regarding the freezer compartment in the refrigerator: If you only have a freezer compartment in your refrigerator, you should use the milk within one to two weeks as the temperature there can fluctuate more.
  • Antibacterial effect: The important vitamins, proteins, and fats are preserved during freezing, but the antibacterial effect is lost after about three weeks.

Information: For premature, very small, or immunocompromised babies, professional associations recommend even stricter times: a maximum of 24 hours in the refrigerator and 3 months in the freezer ≤ -18 °C; all pump parts should be sterilized daily.

Properly thawing and warming frozen breast milk

Patience is important when thawing to ensure the valuable nutrients are preserved.

• Thawing:
  
  
  • In the refrigerator: This is the best method and takes about 12 hours.
  • Under running water: Hold the bottle or bag under cold or lukewarm running water (max. 37 °C).
  • In a water bath: Fill a bowl with warm (not hot) water and place the container with the milk inside. Ensure that no water gets into the milk.
  • With a bottle warmer: You can also use a special bottle warmer, ideally with a thawing function.
  • NEVER thaw or heat in the microwave or in boiling water! This destroys nutrients, can create "hot spots," and burn your baby.
  • Do not refreeze thawed milk.
• Shelf life after thawing:
  
  
  • At room temperature: Maximum two hours after complete thawing.
  • In the refrigerator: Up to 24 hours. An unopened container is good for 24 hours, an opened one for 12 hours.
• Warming:
  
  
  • Is warming necessary? Not necessarily! Many babies enjoy milk at room temperature.
  • Desired temperature: If your baby prefers warm milk, it should be about 35-37 °C (body temperature) .
  • How to warm? Place the milk bottle or bag in a cup, jug, or bowl of lukewarm water (max. 40 °C) for a few minutes. Or use a bottle warmer.
  • Avoid shaking: Gently swirl the bottleto mix the separated fat back into the milk. Vigorous shaking can damage the valuable nutrients.
  • Check the temperature: Place a drop of milk on the inside of your wrist to ensure it is warm, but not too hot.
  • Discard leftovers: Only give your baby as much milk as they need for one feeding. Any leftover milk that has already been warmed or partially consumed should be poured away after one to two hours at the latest.

If breast milk smells strange

Sometimes, cooled or thawed breast milk may smell slightly soapy or rancid. This is normal and is caused by an enzyme called lipase, which breaks down fats. If you have followed all storage guidelines, the milk is perfectly safe for your baby. However, your baby may refuse it due to the altered taste.

If the milk smells soapy: lipase management