Preterm infants face a distinctive physiological challenge. Their organs, including the retina, lungs, brain, and gastrointestinal tract, are still undergoing rapid development when birth interrupts the normal progression of pregnancy. The retina is especially vulnerable because its blood-vessel network is incomplete. After premature birth, exposure to oxygen levels and metabolic conditions outside the womb can disrupt normal vascular growth. Abnormal vessels may then proliferate, leak, or contract, damaging retinal tissue. ROP is therefore not caused by a single factor; it emerges from an interaction between immaturity, oxygen regulation, inflammation, nutrition, and systemic illness.

AA and DHA are long-chain polyunsaturated fatty acids with closely related but distinct biological roles. DHA is a major structural component of retinal and neural cell membranes, helping maintain membrane flexibility and supporting visual and nervous-system development. AA is also incorporated into cell membranes and serves as a precursor for signaling molecules involved in immunity, vascular regulation, and inflammation. The ratio between these fatty acids may matter as much as their individual amounts, because they compete for metabolic enzymes and can be converted into different families of lipid mediators.

That competition creates a biochemical system with potentially important consequences. AA can be converted into prostaglandins, leukotrienes, and related compounds that influence inflammation, blood-vessel behavior, and immune-cell activity. DHA can contribute to specialized pro-resolving mediators, including molecules associated with the controlled termination of inflammation. These pathways are not simply “good” or “bad”: the same lipid network can support normal development in one context and amplify injury in another. In a premature infant, where vascular and immune systems are unusually fragile, changes in fatty-acid availability could alter the balance between inflammatory activation and resolution.

The gut microbiome adds another layer to this picture. The intestinal tract of a preterm infant is colonized by a changing community of bacteria shaped by delivery mode, antibiotics, feeding type, hospital exposure, illness, and gestational age. These microbes can influence host physiology by transforming nutrients, producing short-chain fatty acids, modifying bile acids, and interacting with immune cells in the intestinal lining. Their effects are not confined to the gut. Microbial products and host responses can enter circulation, potentially influencing distant organs, including the developing brain and retina.

The article’s central significance lies in moving beyond a simple association between fatty-acid supplementation, microbial patterns, and ROP risk. A microbiome difference observed in infants with or without ROP does not automatically prove that bacteria caused the eye disease. It may instead reflect prematurity, antibiotic exposure, feeding practices, or the severity of illness. To establish mechanism, researchers must determine whether AA and DHA alter the intestinal microbial community, whether those changes modify measurable metabolites or immune signals, and whether the resulting systemic effects influence retinal vascular development.

This mechanistic approach also highlights why the precise composition of supplementation matters. Nutritional products for premature infants may contain different amounts and ratios of AA and DHA, and infants may receive fatty acids through human milk, fortified milk, formula, or intravenous nutrition. Their bodies may absorb and metabolize these sources differently. A supplement that improves retinal DHA availability could have benefits for visual development, while a shift in AA-derived inflammatory signaling might have separate effects on vascular stability. The final biological outcome may depend on dose, timing, baseline nutrition, genetics, infection, and the infant’s existing microbial ecosystem.

For clinicians, the topic is compelling but not yet a license to change practice based on microbiome theories alone. ROP prevention and treatment currently depend on careful neonatal care, including oxygen management, nutritional support, screening, and established ophthalmic interventions when abnormal vascular growth appears. Any future strategy involving AA:DHA ratios or microbiome-directed nutrition would require rigorous trials that measure more than bacterial abundance. Researchers would need to track lipid mediators, inflammatory markers, retinal outcomes, growth, neurodevelopment, and possible effects on other organs.

The broader message is that preterm nutrition may act as biological information, not merely as a source of calories. Fatty acids can become membrane components, hormones, immune signals, and substrates for microbial transformation. By connecting these layers, Lamadrid-Figueroa’s article presents ROP as a possible example of a condition shaped by the gut–retina axis—a network in which intestinal microbes and their metabolites communicate with distant tissues. The challenge now is to convert intriguing associations into reproducible mechanisms. If that bridge can be built, the microscopic world inside the premature gut could become an important target for protecting sight before retinal damage begins.

Subject of Research: The potential mechanistic relationship between AA:DHA supplementation, the gut microbiome of preterm infants, and retinopathy of prematurity.

Article Title: From association to mechanism: AA:DHA supplementation, the preterm gut microbiome, and retinopathy of prematurity.

Article References: Lamadrid-Figueroa, H. “From association to mechanism: AA:DHA supplementation, the preterm gut microbiome, and retinopathy of prematurity.” Pediatric Research (2026). https://doi.org/10.1038/s41390-026-05376-8

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41390-026-05376-8

Keywords: preterm infants, retinopathy of prematurity, gut microbiome, arachidonic acid, docosahexaenoic acid, AA:DHA supplementation, neonatal nutrition, retinal development, inflammation, gut–retina axis

Preterm infants, born before full maturation of their gastrointestinal and immune systems, are especially vulnerable to conditions such as necrotizing enterocolitis (NEC) and sepsis. The establishment of a healthy gut microbiota in these neonates is a critical determinant of risk reduction for such life-threatening conditions. Human milk—from the infant’s own mother or donor milk—is considered the gold standard for feeding preterm infants due to its unique bioactive components, immunological factors, and essential nutrients. However, donor milk must undergo processing to ensure microbiological safety, predominantly through pasteurization, which can inadvertently alter its beneficial properties.

The study at hand delves into two principal pasteurization methods: Holder pasteurization, which involves heating milk to 62.5°C for 30 minutes, and high-temperature short-time (HTST) pasteurization, which rapidly heats milk to 72°C for 15 seconds. While Holder pasteurization has been the traditional and widely implemented standard in milk banks worldwide, emerging evidence suggests that HTST and other novel techniques may better preserve the functional and microbiological integrity of human milk. Yet, their direct effects on the neonatal gut microbiome remained inadequately characterized until now.

By systematically analyzing stool samples from preterm infants fed with milk subjected to either Holder or HTST pasteurization, the research team employed advanced metagenomic sequencing tools to map the complex communities of bacterial taxa colonizing the infants’ gastrointestinal tracts. The investigators discovered striking differences: infants receiving HTST-pasteurized milk showed significantly increased microbial diversity, with a richer abundance of beneficial genera such as Bifidobacterium and Lactobacillus, organisms known to support gut barrier function and modulate immune responses.

These findings highlight that HTST processing preserves more of the milk’s bioactive molecules and endogenous microbiota, elements believed to foster a more favorable microbial colonization. Conversely, the Holder method, although efficacious at eliminating pathogens, may lead to a depletion of these critical components, potentially resulting in a less diverse and more pathogen-prone microbiome. This could, in turn, explain the observed clinical discrepancies in infant outcomes related to feeding regimens that rely exclusively on Holder-pasteurized milk.

The implications transcend microbiology alone. A richer gut microbiome, nurtured by less disruptive milk pasteurization, is intricately tied to improved nutrient absorption, maturation of the immune system, and reduced incidence of inflammatory diseases in preterm infants. Such outcomes align with the overarching goal of neonatal care: to replicate, as closely as possible, the protective environment of the womb, thereby minimizing the vulnerabilities imposed by premature birth.

The research also meticulously measures critical milk components—such as immunoglobulins, enzymes, and growth factors—before and after pasteurization. HTST methodology retains higher levels of these molecules, reinforcing the notion that rapid heating serves as a gentle yet effective microbial inactivation strategy. The preserved biologically active proteins likely act synergistically with the microbial populations to foster an optimal intestinal milieu conducive to health.

Technological advancements in human milk processing thus stand at a pivotal crossroads. The laborious rigor traditionally associated with Holder pasteurization ensured safety but perhaps at the expense of efficacy. The study underscores a paradigm shift advocating for integration of HTST or other innovative methods, potentially transforming standard operating procedures at milk banks and neonatal units worldwide.

Clinicians and neonatologists stand to benefit immensely from these discoveries, as optimized donor milk could serve as a powerful intervention tool. Enhanced microbial diversity in the gut correlates with lower risks of sepsis and NEC, conditions that carry profound morbidity and mortality. Personalized nutrition based on refined milk preparation could ultimately improve neurodevelopmental outcomes through the gut-brain axis, an increasingly validated concept linking early microbiota composition with cognitive trajectories.

Moreover, the researchers propose that future studies should investigate the long-term impacts of these microbial shifts beyond the neonatal period, encompassing infancy and childhood development. Longitudinal tracking of immune markers and growth parameters would provide further clarity on the lasting benefits of improved pasteurization techniques. Such comprehensive approaches will be essential in establishing evidence-based guidelines consolidating the role of donor milk processing in neonatal care.

Critically, the study’s robust methodology, encompassing rigorous sequencing, biochemical assays, and clinical correlation, sets a new benchmark for neonatal nutrition research. Its pioneering approach blends microbiology, biochemistry, and clinical science, reflecting the interdisciplinary nature of tackling prematurity-associated challenges.

The global burden of preterm birth necessitates innovative strategies that extend beyond survival to thriving. Human milk is integral to this mission. Fine-tuning how donor milk is processed could be a simple yet monumental step in safeguarding the health of the most vulnerable infants.

As milk banking infrastructures adapt, incorporating HTST pasteurization protocols may become more feasible with technological advancements lowering operational costs and improving scalability. Widespread adoption can potentially democratize access to superior-quality donor human milk, especially in regions where maternal lactation is compromised or insufficient.

This transformative research thus opens new horizons, uniting science and clinical practice with compassionate care. While ensuring safety remains paramount, optimizing nutritive and immunological properties through refined pasteurization offers an unprecedented opportunity to harness the full potential of donor human milk.

In conclusion, this landmark study by Ocampo-Chih and colleagues represents a critical leap forward in understanding the complex interactions between milk processing methods and the neonatal gut microbiome. By demonstrating that HTST pasteurization better preserves microbial diversity and bioactive constituents compared to the traditional Holder technique, the findings chart a course toward improved neonatal outcomes globally. The compelling evidence calls for reevaluation of current milk banking standards and underscores the importance of continuing research on nutrition-based interventions in preterm infant care.

Subject of Research: The impact of donor human milk pasteurization methods on the gut microbiome composition and diversity in preterm infants.

Article Title: Impact of donor human milk pasteurization methods on the gut microbiome of preterm infants.

Article References:
Ocampo-Chih, C., Hendricks, H., Weitkamp, S. et al. Impact of donor human milk pasteurization methods on the gut microbiome of preterm infants. Pediatr Res (2025). https://doi.org/10.1038/s41390-025-04386-2

DOI: https://doi.org/10.1038/s41390-025-04386-2