Expert: Sally Wendkos Olds - 10/8/2004

Question
Usually I can express about 2-3oz breast milk for each expressing, but my baby need 4-5oz for each meal. Can I mix breast milk that I pump at two different times? and can I express directly the breast milk into a cool breast milk that was expressed few hours or more (like 1 day) before.
secondly, Can I mix the left-over milk with the newly-expressed milk?

Answer
Dear Memory,

First, congratulations for giving your baby the best start in life by breastfeeding!

When you're ready to feed your baby, you can give her (or him) milk from two different pumpings, mixed together. I would not, however, express new breast milk into refrigerated breast milk. You can do this with previously frozen breast milk, though. And you should not feed your baby milk left over from a previous feeding, because bacteria from the baby's mouth can germinate in the milk. This is why it's always a good idea to use small bottles and freeze the milk in small amounts.

I devote an entire chapter of my book to expressing, storing and feeding breast milk. I'm attaching a brief excerpt below, but there's a lot more you will want to know.

Good luck!

Sally

Sally Wendkos Olds
author, THE COMPLETE BOOK OF BREASTFEEDING: Eiger & Olds, 3rd edition 1999, published by Workman Publishing & Bantam Books, and available in most public libraries, bookstores & La Leche League chapters.
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  BOX 17-3   STORAGE TIMES FOR COLLECTED MILK
Basically, your collected breast milk will keep for several hours at room temperature if it's covered, it will keep in the refrigerator for about two days, and if you want to keep it longer than that, you should freeze it.
  The following guidelines should assure safety and maximum benefit to your baby.
  * To be given to baby within 30 minutes: No special storage needed. Can be kept at room temperature.
  * To be given to baby within 6 to 10 hours: Pour into clean container; cap tightly. You do not have to refrigerate the milk; human milk kept in a capped clean container does not grow bacteria, even at room temperature (66 to 72N F) because of its ability to slow the growth of bacteria. However, if the room temperature is higher than 72N, refrigerate it.
  * To be given to baby within 48 hours (2 days): Pour into clean container; cap tightly. Refrigerate at 40N F (4N C) or below.
  * To be given to baby within a week: Pour into clean container; cap tightly. Quick-cool in the refrigerator for 30 minutes. Then freeze in refrigerator-freezer unit.
  * To be given to baby within 1 to 2 weeks: Pour into sterile container; cap tightly. Quick-cool in the refrigerator for 30 minutes. Then freeze in refrigerator-freezer unit.
  * To be given to baby within 3 to 6 months: Pour into sterile container; cap tightly. Quick-cool in the refrigerator for 30 minutes. Then freeze at 0N F (-18N C) or below in the freezer of a two-door refrigerator or a deep freeze that is not opened often. Not all freezers stay cold enough for long-term storage. Check temperature with a freezer thermometer at different places in the unit. The freezer should maintain a constant temperature of 0N. If it keeps ice cream very solid, it is probably cold enough.
  If your freezer does not get this cold but does keep other frozen foods hard, keep the milk in the center of the freezer and use within three to four months. Frost-free refrigerators, which have a warming element, generally do not maintain 0N.
  To find out whether your milk thaws and then refreezes in your freezer, check by keeping an ice cube in a little jar; if you check it a day later and find that it has melted and refrozen, you'll know that this has probably happened to your milk, too. If so, you'll have to discard the milk.
  It's best to use milk soon after collecting it, and preferably within three months. For one thing, milk collected when your baby is two months old will not meet her needs as effectively when she is six months old.
  * Keeping breast milk longer than 6 months: This is not a good idea. While instructions are sometimes given for keeping frozen milk up to two years, long-term freezing alters the chemical composition of the milk. (Some of the fats break down, and the milk loses some of its ability to fight harmful organisms.) Furthermore, you run the risk of contamination if you lose electrical power during that time and the milk thaws and refreezes.
  * Do not refreeze milk that has defrosted. If frozen milk has started to thaw, refrigerate it immediately and use it within 12 hours.
  END OF BOX
  
HELPFUL SUGGESTIONS
  * Use a nontoxic marker to label each container of frozen milk with the date so you'll be able to use the oldest milk first. If you're taking it to a babysitter, child care center, or hospital, put your baby's name on it.
  * Don't fill bottles or bags to the top. Milk expands as it freezes, so no more than three and a half ounces should go into a four-ounce bottle.
  * You can collect milk a little at a time, chill it in the refrigerator, and add the cold milk to milk that's already frozen. It will have an interesting layered look that will not affect its quality. Be sure to chill the milk first; adding warm milk can defrost the top layer of the frozen milk.
  * You can also freeze milk in a plastic ice-cube tray covered by plastic wrap. The frozen cubes (about half an ounce to an ounce each, depending on the size of the compartments) can then be transferred to an airtight plastic or glass container. When you or your sitter is ready to feed your baby, put the number of cubes you need in a feeding bottle and defrost as below. This way you have more flexibility, since you can defrost only what your baby needs. Since the cubes defrost quickly, it's easy to add another one if your baby still seems hungry.