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Baby Medical Q&A, Issue #088 Expressed Breast Milk Info
February 01, 2014

Welcome to another edition of Baby Medical Q&A News.

Expressing and Storing Breast Milk

I hope 2014 is going well for you all.

This month, I want to discuss the expressing and storage of breast milk.

As you know, breast milk is the best food you can give your infant. The WHO advises breast-feeding infants up until the age of 2 years.

Reasons to Express and Store Milk

There are several reasons you may want to express breast milk and store it to be given at a later time:

  • your baby may be ill or having trouble latching on the breast
  • you may have breast discomfort because you have too much milk
  • you may wish to return to work, so need someone else to feed your baby

Methods of EXpressing Breast Milk

You can choose to manually express milk by squeezing your breasts or you can use a breast pump. Breast pumps may be hand suction pumps or electric pumps.

Manually Expressing

  • Wash your hands with soap and water
  • Hold your breast with your hand shaped like a C with the thumb on the top half of the breast and the fingers holding the bottom half.
  • Gently squeeze the breast and then release. Eventually a few drops of milk will appear. The drops flow more as you continue squeezing
  • Do not squeeze the nipples, rather squeeze the breast tissue
  • Once the flow stops on one breast, change to the other
  • Collect the breast milk into a sterilised container such as a bottle

Using a breast pump

  • Wash your hands with soap and water
  • Follow the directions of the manufacturer
  • If there is discomfort at the start of pumping, use the manual expressing technique until the milk is flowing and then use the pump
  • Collect the milk into a sterilised container

  • Comparing Methods of Expressing Breast Milk

    A review of the literature investigated different methods of expressing breast milk -

    -they looked to see if there was any difference in bacterial contamination between electric and hand expressing. They found no differences.

    -they looked at what helped with producing a good volume, and although some studies suggested more volume with large electric pumps, there were good volumes shown with manual expressing and hand pumps, so I would advise that these are tried first.

    -more milk was expressed if relaxing music was played, so staying relaxed is important whatever method you choose.

    Sterilizing the bottles and pumps

    It is very important to sterilise the bottle which contain the milk and the pump parts if a pump is used. This prevents bacterial contamination, which could potentially cause serious infection in your baby.

    Before sterilizing, make sure you have washed the bottles, teats and pump with soapy water and then rinsed with cool water. Sterilize pumps before and after each use.

    Methods of sterilization include:

    1. Cold Water Sterilizing Solution

    • Follow the manufacturer's instructions
    • Change the solution every 24 hours
    • Keep the bottles and teats etc in the solution for at least 30 minutes
    • Ensure the bottles and teats are under the solution

    2. Steam Sterilizing (Electric or microwave)

    • Follow the manufacturer's instructions
    • Ensure the openings of the bottles and teats are facing downward

    3. Boiling

    • Ensure all items are below the water level
    • Boil for at least 10 minutes
    • Watch out for wear particularly on the teats

    If the bottles and teats are not being used immediately, put the teats on the bottles and put the lids on to prevent bacterial contamination.

    Storing Expressed Breast Milk

    Always store expressed breast milk in a sterilized container, such as a bottle. Mark the date and time the milk was expressed on the container and make sure you use the oldest milk first.

    Expressed breast milk can be stored:

    • in the fridge for up to 5 days at 4 degrees Celsius or lower, but it is best if you can use within 48 hours. Store in the back and in the lower part of the fridge for more consistent temperatures
    • in the freezer for 3 months (if the freezer has a separate door). Milk in a deep freezer can be stored for 6 months
    • in a cooler bag with an ice pack for up to 24 hours if there is no fridge, such as when traveling

    Store the milk in small volumes, such as 100-300 ml, just enough for a feed.

    Do not add freshly expressed breast milk to frozen milk.

    Thawing Frozen Expressed Breast Milk

    You can thaw milk in a couple of ways:

    • Thaw in the fridge over a 24 hour period. Once thawed it can only be kept for 24 hours
    • Thaw by immersing the bottle in lukewarm water - if you thaw in this way, use immediately or you can store in the fridge for up to 4 hours
    • Do not microwave to thaw or warm breast milk

    Using Expressed Breast Milk

    • Once thawed, use within 24 hours
    • Once thawed, if not all the milk is consumed, it can be kept for 1 hour before discarding
    • Do not refreeze breast milk once it has thawed.

    Avoid Bacterial Contamination

    NB. If the milk develops a pink color, this indicates probable infection. Discard the milk and sterilize all the equipment again. Some bacteria produce a pink color and so this is a strong clue that the milk is contaminated. Not all bacteria do this, so the milk may still be contaminated even if a normal color.
    You avoid contamination by:
    • washing your hands before expressing
    • sterilising all the equipment - bottles, teats and pumps before use


    • Becker et al. Methods of milk expression for lactating women. Cochrane Database Syst Rev 2011 (12):CD006170
    • NHS guidance - and-baby/pages/expressing-storing-breast-milk.aspx
    • NZ MOH guidance -
    • Clifford et al. My expressed breast milk turned pink.J Paeds and Child Health 50(2014)81-82

    Please feel free to share this ezine with family and friends.

    Till next time,

    Dr Maud

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