Storing Breast Milk or Formula

This article discusses the following topics about storing breast milk or formula:
Why? Label Formula Storage Breast Milk Storage Use Fresh or Frozen? How to Warm the Milk More Information Works Cited

Why?
Why would you want to store breast milk? I would definitely recommend keeping a reserve of breast milk on hand even if you do not plan to return to work or you plan to solely breastfeed your baby. Something unexpected may come up and you are unable to breastfeed your baby. For example, with my first baby, I got an eye infection and had to go on steroids and it was not recommended to continue breastfeeding and/or I was suppose to limit the amount of breastfeeding. Even if you plan to simply switch over to formula if something happens you wouldn't want to transition immediately from breast milk to formula so it would be helpful to have additional supplies of breast milk. Please refer to the "Formula Transition" article for more information if you are planning to transition from breast milk to formula.

With my first baby I never pumped enough breast milk to have additional supplies and with my second baby I had plenty of frozen reserves. I purposely didn't pump very often as I wanted to produce the amount of milk my baby needed on a daily basis (not overproduce) but occasionally I would collect some additional reserves.
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Label
When storing the breast milk or pre-made formula you will want to make sure it is clearly labeled with the date (possibly time) and whether it is breast milk or formula. I bought colored labels at Office Max. I would write the date and time (am or pm) on the bottles. Breast milk is richest in fat in the morning (after a good night’s sleep), so you may want to save the morning pumped milk to give to the baby before bed to help the baby sleep longer (Hogg 117).   I liked the fact the labels were color coded and so I would use green for breast milk and blue for formula.

By labeling the bottles we ensured we used the old breast milk or formula first and we didn’t worry that an old bottle of breast milk got stuck behind the orange juice and then we gave that bottle to our baby thinking it was a new bottle of breast milk. If you are freezing breast milk, make sure you also label the amount in the freezer bag so you know when it is time to defrost the milk. If you ate something unusual or took any medication at the time of collection of the breast milk you may want to write this on the label as well.
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Formula Storage
According to Nestle Good Start formula you should use an open can within one month. “You need to feed “baby immediately OR refrigerate and use bottles or cups within 24 hours. After feeding begins, discard formula left in bottle or cup within 1 hour.”  I do not think it is recommended to freeze formula.
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Breast Milk Storage
Breast milk can be stored for a short period at room temperature, in the refrigerator, or in the freezer and sources differ on how long you can keep breast milk. Please refer below for guidelines according to the La Leche League International (LLLI).

¹If you do freeze the breast milk, even though according to the LLLI you can keep the milk up to 12 months you may not want to keep the milk longer than six months. Your body produces a different type of milk early in the baby’s life versus later so you would not want to give a nine month old baby breast milk you pumped when he was three months old. According to Eiger, “[i]t’s best to use milk soon after collecting it. Ideally, you will not keep it longer than three months.”  In addition it is not good to freeze the breast milk for an extended period of time since “long-term freezing alters the chemical composition of the milk”  (Eiger 351).

First it is advised to “[q]uick-cool in the refrigerator for 30 minutes (Eiger 351). You can leave the milk in the refrigerator for a few days and technically, you could leave it in the refrigerator for 8 days and then freeze it. I liked to keep to the ideal limit of 72 hours in the refrigerator and then I'd put the milk in the freezer. You will also want to make sure the milk stays completely frozen while in the freezer. Not all freezers stay cold enough for long-term storage…. The freezer should maintain a constant temperature of 0°F. Frost-free refrigerators, which have a warming element, generally do not maintain 0°” (Eiger 351)

When storing in the freezer, it may be best to freeze the breast milk in small quantities, possibly 2-4 ounces. If you store the milk in small quantities it will help when you need to thaw the milk and will hopefully waste less. If your baby did not take a bottle within the first couple weeks, if you try to introduce a bottle at a later date, she may reject the bottle and so you would want to have a small amount of breast milk to give her in a bottle so you do not waste it as it may take awhile until she accepts the bottle.

You can buy disposable plastic storage bags made to store breast milk which are easy to label with the date and the amount. It is not recommended to use the disposable bottle liners or non-breast milk plastic bags since those are less durable and some types of plastic may destroy the nutrients in milk (LLLI). I would also make sure the container is BPA free. When freezing remember the milk will expand as it freezes so leave room at the top of the container to allow for expansion.
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Use Fresh or Frozen
If you have frozen breast milk and you need to give your baby a bottle should you use the fresh milk you pumped that day or use your frozen milk? I liked to do a combination. According to LLLI, "[r]efrigerated milk has more anti-infective properties than frozen milk." Based on that ideally you would want to always use the current refrigerated milk but since your body produces milk differently for a 3 month old baby versus a 6 month old baby eventually you'll want to use the older breast milk as well.

Breast milk may separate into layers, a milk layer and a cream layer when it is stored. As discussed in the "About Breastfeeding" article, there are three different types of breast milk, quencher, foremilk, and hind milk. Simply swirl the milk to re-combine it. According to LLLI, "thawed milk may smell or taste soapy" because of the breakdown of milk fats. "The milk is safe and most babies will still drink it."
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How to Warm the Milk
For bottles made with formula or breast milk from the refrigerator we always warmed the bottles using a bottle warmer. You can also warm the milk by running it under warm water or first heating a pan of water on the stove and then putting the container in the pan. Do not heat the milk directly on the stove. You are not suppose to use a microwave as it "may cause the loss of some of the beneficial properties of the milk" and it "may leave hot spots in the container of milk [or formula]" (LLLI). You do not want to boil the milk.

If the breast milk is frozen, first "thaw in the refrigerator overnight or under cool running water. Gradually increase the temperature of the water to heat the milk to feeding temperature" (LLLI). Both of our babies like to drink the milk warm or at least at room temperature. We always tested the milk on our wrists before giving it to them.
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More Information
Remember that this is an abbreviated version of what I’ve read related to storing of formula and breast milk. The La Leche League web site is a good source for information about storing breast milk. Please refer to “Resources” for all of the resources related to breastfeeding and bottle feeding.
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Works Cited

Eiger, Marvin S. M.D. and Sally Wendkos Olds. The Complete Book of Breastfeeding. New York:
Workman, 1999.

Hogg, Tracy and Melinda Blau. Secrets of the Baby Whisperer: How to Calm, Connect, and
Communicate with Your Baby. New York: Ballantine, 2001.

La Leche League International (LLLI). "What are the LLLI guidelines for storing my pumped milk?"
La Leche League International. 17 Nov 2010 <http://www.llli.org/FAQ/milkstorage.html>.

Last Updated:  November 2010; December 2009