It is important to store milk properly so that it is fresh and maintains its nutritional and anti-infective qualities. Listed below are answers to some commonly asked questions on how to safely store and thaw breast milk.
How long can breast milk be stored?
Breast milk can safely be stored from hours to months, depending on where stored. More specifically, breast milk can be stored:
- At room temperature for 4 to 6 hours at a room temperature of 79 degrees; for up to 10 hours at a room temperature of 66 to 72 degrees; and for 24 hours at a room temperature of 60 degrees.
- In the refrigerator for up to 8 days at a refrigerator temperature of 32 to 39 degrees.
- In the freezer for up to 2 weeks in a freezer compartment contained inside a refrigerator; for 3 to 4 months inside a freezer compartment in a refrigerator with a separate freezer door; and 6 months or longer if stored in a separate deep freezer. Do not store breast milk in the freezer door rack. Milk stored in the door is exposed to a wide temperature changes due to the frequent opening and closing of the freezer door.
What types of containers can breast milk be stored in?
Refrigerated or frozen milk can be stored in the following types of containers:
Glass containers are probably considered the preferred choice for freezing milk because the components of milk are better preserved in glass. However, because glass can break, it may not be as convenient as other options and some day-care centers may not accept glass containers.
Hard-sided clear plastic containers are a good second choice. There are differing opinions regarding if colored containers should be avoided. Some suggest that it's possible that the colored dye from such containers may leak into the milk.
Freezer bags that are specifically designed for storing breast milk are another choice. Of the three storage options, the freezer bags are most prone to leakage. In addition, if the bag is warmed in water, contamination can occur if the water level goes over the top of the bag (water can sometimes seep in through the seal). If you select breast milk freezer bags for storage, some tips to ensure safety include:
- Used a double bag if thinner storage bags are used.
- In the freezer, store all bags containing breast milk in a hard plastic storage container with a lid.
- Do not use ordinary plastic storage bags or bottle liners to store breast milk. Only use the specially designed nursery bags for this task.
- When warming the bag in water, do not allow the water to go over the top of the bag, which might allow water to possibly seep into the bag. If the water used for warming becomes cloudy, a leak has occurred and the bag of milk must be thrown away.
The key point for any option selected is that the container must have tight sealing lid or seam (if using a freezer bag for breast milk).
What quantities of milk should be stored to meet my baby's needs?
Consider storing 2 to 4 ounces of milk per container. This is the average amount of milk consumed in a single feeding. In addition, you may want to store some milk in smaller 1 to 2 ounce increments. This amount is particularly good for babies less than 6 weeks old and can be used as a small snack at any time for babies of any age. Milk stored in this smaller size can be warmed quickly and may cut down on the amount that would otherwise go unused and would need to be discarded.
What milk should be used first?
Always label your milk with the date it was expressed and use the oldest dated milk first. If you bring milk to your baby's day-care center, be sure your baby's name is clearly visible to avoid mix-ups.
How should milk be thawed and warmed?
First, don't be alarmed by the appearance of your milk. It's normal for stored milk to separate into a cream and a milk layer. It's also normal and safe for breast milk to appear in a range of colors—from slightly yellow to yellow orange, to pink, to green—depending on what you eat, drink, or any medications taken. Thaw and/or heat milk by running it under warm running water for a few minutes or swirling it in a bowl of warm water. After the milk is warmed, gently shake the container to mix its components back together. To test the milk's temperature, spill a droplet or two on your wrist. If the milk is slightly warm (and not hot) it's okay to give to your baby.
Do not use a microwave oven to heat breast milk. A microwave does not heat breast milk evenly and may scald your baby, destroy important proteins and vitamins in the milk, or cause the bottle to explode if left in too long. Also, never warm the container or bag of milk directly on the stove. Heat the pan of water on the stove, remove the pan from the stove, then place the container into the warm water. High heating may lower some nutrient levels. Do not bring the temperature of milk to a high heat or boiling point.
How long can thawed milk be safely used?
If milk has been frozen and thawed it can be refrigerated for up to 24 hours for later use. It should not be refrozen. There is very little evidence to know if stored, warmed, and partially consumed milk can continue to be used. One study suggests that it is safe to continue to feed previously used milk up to 1 to 2 hours after it has been prepared. Any unused milk should then be discarded.
Other final tips:
- Wash your hands before expressing or handling your milk.
- Use containers that have been washed in hot, soapy water and rinsed.
- Freeze breast milk if it will not be used within 24 hours.
- Cooled milk can be combined with other cooled or frozen milk as long as the quantity of cooled milk is small enough that it doesn't thaw a frozen batch.
- Always date the milk before storing.