Donor human milk is a lifeline for premature babies when a mother’s own milk isn’t available. But how long that milk has been stored may make a big difference in protecting fragile newborns from gut disease.
Researchers at the Medical University of South Carolina reviewed the medical records of 262 very-low-birth-weight infants who received donor milk in the neonatal intensive care unit. They found that every additional day of storage increased the risk of necrotizing enterocolitis (NEC), a life-threatening intestinal disease, by 3.7%.
“Our results showed that babies weren’t as protected with the use of donor milk that was stored for a longer time as with donor milk that was stored for shorter periods of time,” said neonatologist and study lead Dr. Katherine Chetta.
NEC is a devastating condition that affects mostly preemies, causing inflammation and even death of intestinal tissue. It can require surgery and often leads to lifelong complications. While doctors have long known that donor milk reduces NEC risk compared to formula, this study suggests that fresher milk may offer stronger protection than milk stored for longer periods.
Lab analyses revealed that certain protective components of milk degrade over time in frozen storage. The “sweet spot” for maintaining protection in extremely low-birth-weight infants was about 240 days, or roughly eight months.
“When preemies are on the edge of viability, and extremely low birth weight, that’s when they seem to be the most susceptible to the effects of storage and can be most protected by having fresher milk,” Chetta said. “Fresh milk is the best.”
Current guidelines from the World Health Organization and U.S. Centers for Disease Control and Prevention allow donor milk to be frozen for up to a year. Chetta and her team suggest that these standards may need to be revisited, at least for the most vulnerable infants.
In the meantime, the findings are already influencing practice at Chetta’s hospital, where staff are prioritizing fresher donor milk for the tiniest babies.
“We’re so convinced that we need a little bit fresher that we’re already doing it just to be on the safer side,” she said.
This study, published in the Journal of Parenteral and Enteral Nutrition, was supported by the U.S. National Institutes of Health, including grants from the National Center for Advancing Translational Sciences and the Digestive Disease Research Core Center at the Medical University of South Carolina. Additional support came from the David and Laura Stone Endowment for Advancement in Neonatal Medicine.