Milk matters: How donor human milk storage affects preemie gut health

A study from the Medical University of South Carolina, published in the Journal of Parenteral and Enteral Nutrition, reveals that shorter storage durations of donor human milk are linked to reduced gastrointestinal complicatoins in premature infants, including necrotizing enterocolitis. These findings suggestt that minimizing milk storage time may help to preserve protective properties crucial for preterm gut health, offering new insights into neonatal nutrition practices and improving outcomes for vulnerable newborns.

Odds are that when you go to the supermarket, you check each product you pick up for its “best by” date, ensuring that you have the freshest, healthiest food to bring home for you and your family. An MUSC study published in the Journal of Parenteral and Enteral Nutrition has found that those little best by dates for a particularly precious resource – donor human milk – have huge implications for the gastrointestinal health of very premature infants.

“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 physician-scientist Katherine E. Chetta, M.D., who led the study. Chetta’s research program is focused on the science of breast milk, nutrition and intestinal rehabilitation.

Donor human milk is a vital substance, given to almost all preterm babies, especially if their own mother’s milk is unavailable, in short supply or otherwise unsafe. It can also reduce complications associated with formula, while supporting immune function, digestion and infants with specific medical conditions, such as low blood sugar, congenital heart disease and immunologic deficiencies.

Perhaps one of the greatest benefits of using donor milk is to reduce the risk of necrotizing enterocolitis, or NEC, as it’s often referred to in neonatal intensive care units (NICUs), where most pre-term babies are cared for. NEC is a very serious inflammatory disease that affects mostly preemies and can lead to bowel tissue dying. It requires medication and often surgery and can lead to lifelong complications.

Although doctors and scientists have not yet identified the sole cause of NEC, they do have some ideas about several factors that, together, can cause injury to the premature gut, allowing bacteria in and creating inflammation.

As a neonatologist at the MUSC Shawn Jenkins Children’s Hospital, Chetta has long dealt with the devastating effects of NEC in her patients. “It's one of those key benchmark diseases that all NICUs are constantly trying to decrease,” she said.

As a physician-scientist, Chetta collaborates closely with the nutrition management center or “milk room,” where the donor milk is stored. Based on previous studies and detailed analysis of the milk, Chetta and her team knew that longer storage times mean a breakdown in the action and efficacy of specific milk components. Chetta wondered whether aging milk is less protective against the development of NEC than fresher milk.

To determine the answer, she reviewed the medical records of 262 very-low-birth-weight, less than 3.3 pounds, infants who were provided donor milk in the NICU at the MUSC Shawn Jenkins Children’s Hospital between February 2022 and January 2024. Of those premature babies, 226 remained free of disease while 36 developed NEC or another gut disease called spontaneous perforation, which also causes tremendous damage to intestinal tissue. The South Carolina Clinical & Translational Research Institute, a Clinical and Translational Science Awards hub with an academic home at MUSC, provided statistical support for the .

Chetta’s findings revealed that every additional day of storage increased the risk of NEC in very-low-birth-weight preemies by 3.7%. The sweet spot for frozen milk storage was approximately 240 days for the tiniest infants. Laboratory results showed that, over time, certain milk components degrade even while in frozen storage.

"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," explained Chetta. In short, for preemies: “Fresh milk is the best.”

Currently, the World Health Organization and Centers for Disease Control and Prevention both advise that frozen milk can be stored safely for up to a year for all babies. Based on this study, Chetta and her team believe that these guidelines need to be reevaluated, especially regarding critically ill babies. Still, this laboratory finding has already influenced clinical practice in Chetta’s NICU.

“We're so convinced that we need a little bit fresher that we're already doing it just to be on the safer side,” said Chetta, of feeding high-risk, premature infants the freshest milk possible based on the study results. “That's how much we believe in it.”

The practical application of this finding doesn’t mean discarding or wasting milk that is considered not quite as fresh but, rather, using fresh milk more quickly and optimizing freezing and storage procedures so that the sickest and youngest babies can have the freshest milk. To achieve these goals, Chetta worked closely with the Mother’s Milk Bank of South Carolina and others involved in the handling of human milk.

Based on her experience, she can offer some simple, easy-to-follow advice: “Other NICUs could talk to their own milk banks about bringing this milk in a little bit quicker from donor depot sites, as we did.” Chetta said it really is as simple as that. “We didn't have to change much. We were just refocused on trying to get it under that threshold of 240 days.”

While this is still very new information, Chetta and her team have high hopes for its impact in the not-so-distant future. “I think improving outcomes can be expanded very rapidly once people start verifying some of the findings we have,” she said. “From a policy standpoint, it could be a quick change. I hope the use of fresher milk will make a difference in the lives of the youngest babies. I think it will.”

# # #

About the Medical University of South Carolina

Founded in 1824 in Charleston, MUSC is the state’s only comprehensive academic health system, with a mission to preserve and optimize human life in South Carolina through education, research and patient care. Each year, MUSC educates over 3,300 students in six colleges and trains more than 1,060 residents and fellows across its health system. MUSC leads the state in federal, National Institutes of Health and other research funding. For information on our academic programs, visit musc.edu.

As the health care system of the Medical University of South Carolina, MUSC Health is dedicated to delivering the highest-quality and safest patient care while educating and training generations of outstanding health care providers and leaders to serve the people of South Carolina and beyond. In 2025, for the 11th consecutive year, U.S. News & World Report named MUSC Health University Medical Center in Charleston the No. 1 hospital in South Carolina. To learn more about clinical patient services, visit muschealth.org.

MUSC has a total enterprise annual operating budget of $8.2 billion. The nearly 34,000 MUSC members include world-class faculty, physicians, specialty providers, scientists, contract employees, affiliates and care team members who deliver groundbreaking education, research and patient care.

About the South Carolina Clinical & Translational Research Institute

The South Carolina Clinical & Translational Research (SCTR) Institute is the catalyst for changing the culture of biomedical research, facilitating the sharing of resources and expertise and streamlining research-related processes to bring about large-scale change in the clinical and translational research efforts in South Carolina. Our vision is to improve health outcomes and quality of life for the population through discoveries translated into evidence-based practice. To learn more, visit https://research.musc.edu/resources/sctr