All About Breast Milk Storage and Preparation

Choosing to breastfeed is the best way to ensure optimal health and development for your baby. If you need more flexibility with your work or other commitments, you will need to use a breast pump and learn how to store the expressed milk for later use.

Key takeaways:
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    It is safe to store breast milk as long as you follow the safety guidelines.
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    Breast milk can be stored at room temperature, in the refrigerator and freezer.
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    For optimal benefits choose baby safe containers and make sure the tools are properly cleaned and sanitized.

Breast milk preparation

Mothers can express breast milk using a breast pump or by hand. You should inspect the pump to make sure it is clean and wash your hands with soap, water or a sanitizer with at least 60% alcohol.

Freshly-expressed milk

Expressed milk can be served cold or at room temperature. If you choose to warm the milk, keep the container sealed and place it in a bowl of warm water. Do not use the stove or the microwave. Put a few drops on your wrist to make sure the milk is not too hot.

If the baby does not finish the bottle, the leftover milk should be used within two hours.

Thawed, previously frozen breast milk

First in, first out. Thaw the oldest milk first, because the quality of milk and nutrient content, particularly vitamin C, decreases over time.

Thaw the breast milk in the refrigerator during the night (and use it within 24 hours) or place it under lukewarm running water. Do not use a microwave because some nutrients are destroyed and there is a risk of hot spots that can burn the baby’s mouth.

Once the breast milk is warmed or at room temperature, it should be used within two hours. Do not refreeze thawed breast milk.

Thawed breast milk may have a different odor or consistency compared with freshly-expressed milk, and this is normal. The color of the milk may also be influenced by your diet. If the baby refuses thawed milk, consider storing the milk for shorter periods of time.

Freshly-expressed milk can be combined with previously frozen or refrigerated milk. In this case, the fresh milk should be cooled in the refrigerator or in a cooler with ice before adding it to frozen milk. Warm breast milk should not be combined with frozen milk.

Breast milk storage guidelines

Below are the recommendations from the Centers of Disease Control and Prevention (CDC) regarding breast milk storage:

  • Freshly expressed or pumped breast milk can be stored for up to four hours at room temperature (77°F/25°C or colder) and up to four days in the refrigerator at 40°F/ 4°C. The breast milk can be stored in the freezer (0°F /-18°C or colder). In this case, it should be consumed ideally within six months, but no longer than 12 months.
  • Thawed, previously frozen breast milk can be stored for one to two hours at room temperature and up to 24 hours in the refrigerator. Refreezing is not an option. Breast milk should never refreeze after being thawed.
  • If the baby did not finish the bottle, the leftover can be consumed within two hours after the baby finished feeding.

What are the safest containers to store breast milk?

Choose clean, capped food grade containers that have tight fitting lids. The general recommendation is to use glass or BPA-free plastic containers. Although the chemical bisphenol A (BPA) is mostly known to be associated with health issues, other bisphenols, phthalates and other chemicals found in plastic had been linked with various concerns, including hormonal disruptions and cancer.

If glass containers are not an option, look for eco-friendly products available online or in health food stores, but avoid using disposable bottles or bags that are not intended for storing breast milk.

When it comes to baby-safe bottles, the Environmental Working Group (EWG) suggests using glass bottles as the best choice. Safe plastics for bottles and sippy cups are made of polyethylene, polypropylene or polyamide. Silicone bags are another good option. It is best to avoid clear, hard plastic bottles marked with the number seven or "PC."

Medela breast pump tubes, shields, and jars are safe options, as these products are doctor approved, BPA and phthalate free.

Label the bottles with waterproof ink, including the date when the breast milk was expressed and the baby’s name if the bottle is used in a childcare.

Place the breast milk containers in the back of the refrigerator or freezer because this is where the temperature is the lowest. Avoid storing breast milk in the door of the freezer or the refrigerator because the temperature changes from door opening. If a fridge is not available, the milk can be stored in insulated coolers with ice packs for up to 24 hours, then stored in the refrigerator or freezer.

Keep in mind that breast milk expands when it is frozen, so do not fill the containers to the brim. Store milk in two to four ounce portions to prevent waste and also have handy a few smaller portions of one to two ounces for any unexpected situations or changes in the feeding schedule.

Keeping the breast pumps and containers clean

Germs can quickly grow and contaminate breast milk or may remain on the pump and containers. The following steps can prevent milk contamination:

  • Store the milk safely. Place the container in the refrigerator immediately after collecting the milk.
  • Clean the pumping area with disinfectant wipes.
  • If cleaned by hand, take apart the pump kit, rinse the parts that came in contact with milk under running water. Next, clean the parts with soap and water. Scrub the pump parts, rinse under running water and let them air dry. If the pump kit manufacturer recommends cleaning in a dishwasher, wash the parts according to the instructions. It is important to wash your hands with water and soap before handling cleaned items. Use a paper towel to air dry the parts before storing them.
  • To add another layer of protection against germs, consider sanitizing the pump parts once a day. Sanitizing may not be needed for older babies in good health, but is recommended for premature babies or those with weakened immune systems. The pump kit, the bottles, the brushes, and the wash basin should be sanitized according to the manufacturer’s instructions which may recommend either steaming or boiling the parts.

Babies can be safely fed with stored milk, as long as the parents use the guidelines for proper storage, clean the parts properly and choose baby safe containers. Consult a healthcare professional who specializes in breastfeeding, especially if your baby was born prematurely or has a medical condition, as additional rules for milk storage may be recommended.


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