Pooling Expressed Milk

A recent article in “Motherly” touted a new, unannounced change in breastmilk storage guidelines for the American Academy of Pediatrics (AAP). (You can find the AAP information under Frequently Asked Questions under, What are the milk storage guidelines? Evidence suggests mothers can mix warm milk and cold.)

Those links direct you to a research study by Dr. Lisa Stellwagen of UCSD from 2012 of 19 NICU infant mothers who pooled their pumped milk in 24-hour batches one week, and in individual pumping containers the next week. They concluded that 24-hour pooling of human milk reduced the nutrient and caloric variability without increasing bacterial counts.


For NICU and premature babies, consistency of nutrients and caloric content may be a benefit, but for full-term healthy babies, I am not so sure. Mother nature/evolution did not make all human milk the same. One mother’s milk is tailored to the needs of her own infant, changes over time post-delivery, changes over time of day and even
changes with the sex of the child!

As a scientist, I believe there must be a reason why nitrogen (protein) content tends to be highest in the afternoon and evening, and fat content (calories) highest in the early morning! Pooling 24 hours of human milk and
adding warm to already cold expressed milk appears safe in terms of bacterial content, but will it alter any other bodily systems, like hormone cycling or the immune system?

I wonder…

Nancy E. Wight, MD, IBCLC, FAAP, FABM
San Diego, CA, USA

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