Photo by Mariel and Joey Lifestyle Photography
UPDATE
In September 2021, the AAP removed the below guidance from their Frequently Asked Questions page within 24 hours of this post. While they did not retract their original statement, we understand that this change may be confusing. We'll continue to keep up on AAP guidance.
Breastfeeding Guidelines
We are always working to provide moms with the most up-to-date information so they can make decisions for themselves and their babies that are best for their families. We wanted to let you know that the American Academy of Pediatrics previously updated their recommendation regarding adding freshly expressed milk to chilled milk. In September 2021, the AAP replaced the text with links to the older version of the Academy of Breastfeeding Medicine's protocol #8 on Human Milk Storage and the CDC's related guidelines based on the same protocol. You can find those links and a helpful article cited by the AAP here:
📌 Academy of Breastfeeding Medicine Protocol #8 on Human Milk Storage
📌 CDC Guidelines on Proper Breastmilk Storage & Preparation
📌 Healthy Children’s Article on Freezing & Refrigerating Breastmilk
None of the AAP, CDC or ABM sources state that there is any danger in combining temperatures. So the next logical question moms ask is: what happens if I combine milk from different pumping sessions without cooling it first? The answer given by the CDC and the Academy of Breastfeeding Medicine is that combining milk "can rewarm the older stored milk." That's it. That's the answer. No other risks are identified. No research is cited by any sources to indicate that there are additional risks or concerns to be aware of.
This has led to confusion among breastfeeding moms, but here’s what’s important:
None of these sources (AAP, CDC, or ABM) state that there is any danger in combining breastmilk at different temperatures.
So, Is It Safe to Combine Fresh & Chilled Breastmilk?
The CDC and Academy of Breastfeeding Medicine state that combining milk from different pumping sessions "can rewarm the older stored milk."
That’s it.
No other risks are identified, and no research has been cited that suggests additional concerns.
In February 2021, the Academy of Breastfeeding Medicine confirmed this guidance:
Mothers can mix warm milk and cold, or even consider pooling milk from 24 hours together, which may help even out variability in nutrients due to pumping time or breast emptying (which influences fat content of the milk).
For pumping moms already juggling so many rules, this formal recognition is a relief. It validates the ongoing research conducted by renowned pediatricians and biochemists who specialize in human milk medicine.
While updates to these guidelines may take time to appear on major platforms (we recognize the CDC is a little busy these days!), this is a huge step forward for breastfeeding families.
The Science Behind Safe Breastmilk Storage
Research continues to show that breastmilk is unique—it’s not just a food, but a living substance with incredible antimicrobial and immunological properties.
🔬 Scientific Findings:
Human milk contains many known antimicrobial and immunomodulatory molecules... The reduced pH caused by these bacteria [in breastmilk], and additionally, by known and unknown components of human breast milk, make it more difficult for potentially pathogenic organisms to colonize.
Simply put, breastmilk fights bacteria naturally—helping prevent contamination and maintain safety.
Every time guidelines evolve to reflect the latest research, it benefits moms and babies worldwide.
Exciting News: The Human Milk Institute
We’re thrilled to share that Lisa Stellwagen, MD, FAAP, a leading researcher on combining different milk temperatures, has helped launch the Human Milk Institute in San Diego!
This groundbreaking initiative brings together some of the world’s top scientists to:
✔ Advance human milk research
✔ Study best breastmilk storage practices
✔ Explore the impact of pooling breastmilk on newborn health
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