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Updated: May 18, 2026
Individualized Reconstitution of Human Milk Microbiota: A Feasible Approach in Real-World Settings
Published on: February 7, 2025
Pooling expressed breastmilk to provide a consistent feeding composition for premature infants
Lisa M Stellwagen1, Yvonne E Vaucher, Christina S Chan
1Division of Neonatology, Department of Pediatrics, University of California San Diego Medical Center, San Diego, California 92103-8774, USA. lstellwagen@ucsd.edu
Objective:
We hypothesized that pooling a mother's expressed breastmilk for 24 hours compared with individual pump session collection of milk would provide a more consistent caloric product without increasing bacterial contamination.
Study Design:
We investigated 24-hour pooled breastmilk collection by enrolling 19 mothers who were expressing milk for their infants. Mothers followed a standardized milk collection protocol for 4 study days: daily milk was pooled in a sterile 1-L bottle on Day 1, and on Day 2 milk was aliquoted for each pump session into a sterile 120-mL container. The next week the order of collection was reversed. Milk samples were plated, incubated, and evaluated for bacteria colonization. Milk samples were analyzed for protein, fat, and carbohydrate content.
Results:
There was inherently less variability in the caloric and nutrient content of pooled milk compared with individual samples, in which caloric density varied by as much as 29%. Mother's milk had highly variable bacterial counts ranging from 0 to greater than 100,000 colonies/mL. High bacteria counts (>100,000 colonies/mL) occurred in 14.7% (31 of 211) of individual samples compared with 8.6% (three of 35) of pooled samples (p=0.39).
Conclusions:
Twenty-four-hour pooling of human milk reduces nutrient and caloric variability without increasing bacterial counts.
