Prematurity can alter nearly every stage of host defence. Infants born before term may have lower concentrations of maternally transferred immunoglobulin G, because a substantial proportion of placental antibody transfer occurs late in pregnancy. Their skin and mucosal surfaces are also less mature, while their respiratory systems are more susceptible to inflammation and impaired clearance of pathogens. In addition, many preterm infants require prolonged hospital care, respiratory support or repeated medical procedures, all of which can increase opportunities for exposure to infectious agents. Viral illnesses that are relatively mild in older children can therefore cause bronchiolitis, pneumonia, feeding difficulty, dehydration or prolonged hospitalisation in infants born prematurely.

Breast milk contains more than calories, proteins and fats. It is a complex biological fluid carrying antibodies, immune cells, cytokines, oligosaccharides, antimicrobial proteins and molecules that help regulate inflammation. Secretory immunoglobulin A, or sIgA, is particularly important at mucosal surfaces. Rather than circulating primarily through the bloodstream, sIgA can bind pathogens in the mouth, throat and gastrointestinal tract, limiting their attachment to epithelial cells and reducing the likelihood that viruses will cross the mucosal barrier. Human milk oligosaccharides can also act as decoys for microbes and support beneficial bacterial communities in the intestine, potentially influencing the development of systemic and mucosal immunity.

The study’s central exposure is breastfeeding status up to six months of age, a period that includes major changes in infant feeding and immune maturation. In a cohort design, researchers follow a defined group of infants over time and compare health outcomes according to an exposure measured during the study period. Here, the outcome of interest is the incidence of viral infections during the first year of life. This approach is useful because it can capture infections as they occur rather than relying entirely on parental recall after the fact. It may also allow investigators to examine whether an association persists beyond the immediate neonatal period, when breastfeeding and hospital-based care are closely intertwined.

The relationship between breastfeeding and infection is biologically plausible but scientifically difficult to interpret. Infants who receive breast milk may differ from those who do not in many ways unrelated to milk itself. Maternal health, socioeconomic conditions, access to lactation support, mode of delivery, household crowding, exposure to siblings, vaccination, smoking exposure and the severity of the infant’s prematurity can all affect infection risk. The need for neonatal intensive care may influence both the ability to breastfeed and the likelihood of encountering respiratory viruses. For this reason, a multicenter cohort can be valuable: data collected across different hospitals and clinical settings may provide a broader picture than a single-unit study, although observational research cannot by itself prove that breastfeeding directly prevents infection.

The investigators’ focus on viral infections is especially relevant because viruses remain a major cause of respiratory and gastrointestinal illness in the first year of life. Respiratory syncytial virus, influenza, rhinoviruses, adenoviruses, human metapneumovirus and other respiratory pathogens can be consequential for preterm infants, whose smaller airways and limited pulmonary reserve may magnify the effects of inflammation and mucus production. Gastrointestinal viruses can be equally disruptive, particularly when vomiting or diarrhoea compromises hydration and nutritional recovery. The biological effects of breast milk may differ according to the virus, the route of exposure and whether protection occurs through direct neutralisation, altered microbial ecology or modulation of the infant’s inflammatory response.

A key scientific issue is how breastfeeding status is defined. “Breastfeeding” can refer to exclusive breastfeeding, predominant breastfeeding, any breast milk intake or a combination of breast milk and formula. These categories may have different biological implications. The volume and duration of milk exposure may also matter, as may whether the infant receives fresh milk, expressed milk or donor milk. For preterm infants, feeding is often interrupted by medical instability, and some infants transition gradually from tube feeding to oral feeding. A careful analysis therefore needs to distinguish the timing and continuity of breast-milk exposure from the broader clinical circumstances surrounding birth and hospital discharge. The study’s stated six-month window highlights the importance of these details in evaluating longer-term associations.

The findings from this research may help clinicians refine infection-prevention counselling for families of preterm infants, but they should be interpreted within the limits of the evidence reported. The available study description identifies the objective and design but does not provide numerical results, infection-specific estimates or conclusions about causality. It therefore cannot support a claim that breastfeeding eliminates viral infections or that every preterm infant who receives breast milk will experience fewer illnesses. Breastfeeding support must remain individualised, respectful and medically appropriate, particularly when mothers face illness, medication use, low milk production, psychological stress or barriers to expressing milk. When direct breastfeeding is not possible, expressed maternal milk may still provide many of the same biological components, while donor milk and specialised formulas may be clinically necessary alternatives.

By examining viral infections across the first year rather than only during the neonatal admission, the multicenter cohort study places breastfeeding within the broader timeline of infant immune development. Protection in early life is rarely determined by one factor. Maternal antibodies, vaccination, infection-control practices, ventilation, hand hygiene, household exposure and timely medical care all contribute to risk. Breast milk may form one layer in this defence system, supplying locally active antibodies and immune-regulating compounds during a period when the infant’s own responses are still being calibrated. The significance of the work lies in testing that possibility in preterm infants, a group for whom even modest reductions in viral illness could have meaningful consequences for respiratory health, growth and hospital use. Further studies, including analyses that clarify viral species, feeding intensity and potential confounding factors, will be needed to determine how strongly breastfeeding status predicts infection and which mechanisms are most important.

Subject of Research: Breastfeeding and viral infections in preterm infants

Article Title: Breastfeeding and viral infections in preterm infants: a multicenter cohort study

Article References: Kamiya, Y., Takeuchi, A., Nakamura, K. et al. Breastfeeding and viral infections in preterm infants: a multicenter cohort study. Pediatric Research (2026). https://doi.org/10.1038/s41390-026-05373-x

Image Credits: AI Generated

DOI: 10.1038/s41390-026-05373-x

Keywords: breastfeeding, preterm infants, viral infections, infant immunity, human milk, respiratory infections, multicenter cohort study, neonatal health

The study, led by researchers Marshall, Tapia, Dominguez, and their colleagues, embarked on an ambitious evaluation of risk-adjusted mortality and morbidity rates across multiple centers participating in the NEOCOSUR network. This collaborative, multi-national consortium comprises several NICUs from South America, each contributing valuable data pertaining to VLBWI outcomes. What sets this investigation apart is its unique approach to analyzing these outcomes not as isolated events but as interconnected phenomena that collectively influence infant prognosis and the quality of NICU care provided.

VLBWI are subject to an array of severe morbidities, including but not limited to bronchopulmonary dysplasia, severe intraventricular hemorrhage, necrotizing enterocolitis, and retinopathy of prematurity. Clinically, these conditions are often interrelated and are known to contribute significantly to the risk of death in this delicate population. Historically, many neonatal research networks have independently monitored mortality rates and morbidity frequencies, which, while informative, may have obscured the intricate balance between survival and the burdens of serious complications. The NEOCOSUR study goes further by integrating these metrics, offering a comprehensive risk-adjusted model that accounts for the co-occurrence of morbidities and mortality.

The data analysis utilized in this study is noteworthy for its sophistication and depth. The researchers applied advanced risk adjustment methodologies capable of correcting for several confounding variables including gestational age, birth weight, sex, and the presence of antenatal risk factors. This adjustment is crucial to ensure that differences in outcomes are reflective of actual care quality and not simply underlying patient population differences. With these corrections, the study identified patterns of association between mortality and specific severe morbidities that varied significantly from center to center, underscoring the multifaceted nature of neonatal care challenges.

One of the study’s most remarkable findings is that centers with higher-than-expected mortality rates do not necessarily align with elevated morbidity rates. In fact, some centers demonstrated paradoxical trends where mortality appeared relatively low despite substantial morbidity burdens. This suggests that variabilities in clinical practice, early intervention policies, and possibly resource availability might influence survival rates independently of morbidity prevalence. Such insights challenge neonatal networks to reconsider current benchmarking metrics and to develop holistic indicators that truly reflect infant health trajectories.

Furthermore, the investigation delved into the implications of these associations for clinical decision-making. Neonatologists often face the dilemma of balancing aggressive interventions designed to reduce mortality against the risk of exacerbating long-term morbidities. The findings imply that management protocols must be nuanced and adaptable, taking into account the possible trade-offs between survival and quality of life. This could influence critical choices such as the timing of respiratory support, surgical interventions, and nutritional strategies, with an eye toward optimizing both short- and long-term outcomes.

In addition to clinical ramifications, the study illuminates important epidemiological trends. Geographic and socioeconomic factors, inherent to the diverse centers in the NEOCOSUR network, appear to modulate the relationship between mortality and morbidity. These factors may include disparities in healthcare infrastructure, access to highly specialized personnel, and availability of advanced medical technologies. Such disparities highlight the need for region-specific policies and resource allocation that address inequities and promote uniform standards of neonatal care quality.

The NEOCOSUR researchers also advocate for the expansion of integrated data registries that encompass detailed morbidity and mortality information in tandem with demographic variables. A larger data infrastructure, coupled with real-time analytics, could enable healthcare providers to monitor risk-adjusted outcomes dynamically. This would facilitate early identification of centers underperforming or excelling, allowing targeted quality improvement initiatives to be enacted and evaluated effectively. This approach aligns with broader trends in precision medicine and data-driven healthcare innovation.

Importantly, the study emphasizes methodological rigor and transparency in outcome reporting across NICUs. By standardizing definitions for major morbidities and uniformly applying risk adjustment techniques, the comparability of data across centers is enhanced. This standardization is a critical step forward in creating reliable benchmarks, enabling more meaningful inter-center comparisons ultimately leading to improved care delivery standards on a global scale.

The authors highlight that the multifactorial nature of both mortality and severe morbidity in VLBWI necessitates multidisciplinary collaboration. Neonatologists, nurses, respiratory therapists, surgeons, and rehabilitation specialists must work cohesively in continuous communication to tailor interventions that reflect evolving risk profiles. Such teamwork is vital not only in the acute neonatal phase but also throughout the continuum of care extending into subsequent developmental periods.

Looking ahead, the study’s findings open multiple avenues for future research. One promising area is the exploration of genetic and biomarker-based predictors of morbidity and mortality that could fine-tune risk stratifications further. Integrating molecular data with clinical risk adjustment models may reveal hitherto unrecognized risk factors and therapeutic targets. Similarly, the impact of emerging technologies such as artificial intelligence and machine learning in forecasting outcomes and personalizing care strategies deserves concerted investigation.

Moreover, the ethical dimensions of neonatal care surfaced by this research merit deliberation. With evidence suggesting differential survival and morbidity profiles across centers, questions about resource prioritization, informed consent, and parental counseling become increasingly salient. Policies must ensure that all infants have equitable opportunities for survival with the best possible quality of life, regardless of their birth hospital or socioeconomic context.

This multicenter NEOCOSUR study thus represents a seminal contribution to neonatal medicine, bridging gaps between mortality statistics and morbidity realities. By elucidating complex interdependencies under a risk-adjusted lens, the research equips clinicians and policymakers alike with invaluable knowledge. Devising strategies that reflect this intricate balance will be essential to advancing outcomes for the most fragile neonatal patients and setting a new global standard for VLBWI care.

In conclusion, as the global neonatal care community strives to navigate the dual imperatives of reducing death and minimizing severe morbidities, this comprehensive investigation serves as a beacon. It underscores that survival cannot be the sole metric of success; rather, a holistic view encompassing morbidity is indispensable. The lessons drawn from the NEOCOSUR network’s experience reiterate the importance of continuous quality assessment, integration of robust data analytics, and collaborative multidisciplinary care. Ultimately, these advances hold promise for transforming VLBWI prognoses worldwide, heralding a future in which more infants not only survive but thrive.

Subject of Research: Very low birth weight infants (VLBWI) mortality and severe morbidity relationship in neonatal intensive care units (NICUs).

Article Title: Association between risk-adjusted mortality and severe morbidity in very low birth weight infants: a multicenter study from the NEOCOSUR network.

Article References:
Marshall, G., Tapia, J.L., Dominguez, A. et al. Association between risk-adjusted mortality and severe morbidity in very low birth weight infants: a multicenter study from the NEOCOSUR network. J Perinatol (2026). https://doi.org/10.1038/s41372-026-02604-1

Image Credits: AI Generated

DOI: 13 March 2026