A Systematic Review on the Influence of Feeding Expressed Mother’s Own Milk Using Varying Expression Practices or Treatments on Health and Growth of Recipient Infants

when feeding at the breast is not possible, infants can still receive expressed mother's own milk (MOM). Method of expression, hygiene practices and settings during expression, and processing can affect MOM composition. to review current evidence on the influence of feeding expressed MOM using varying expression methods, varying hygiene practices or settings during expressions, or varying treatments on health and growth of recipient infants. we systematically searched CENTRAL, CINAHL, ClinicalTrials.gov, Embase, Emcare, EU trials, Global Health, Global Index Medicus, MEDLINE, Scopus, Web of Science, WHO, for primary research studies, including observational studies, published up to March 2024 evaluating different methods of MOM expression, hygiene practices or settings during expression, processing of MOM, and reporting clinical outcomes on recipient infants. Key outcomes of interest were growth, mortality, morbidity, feeding tolerance, adverse events, CMV infection, retroviral infection, other infections, nutrient deficiencies, neurodevelopment, breastfeeding. Qualitative thematic synthesis was conducted. An evidence gap map was produced using a GRADE evaluation. Of 29,320 studies screened, 45 met inclusion criteria. No expression method or pump type showed clear benefits for breastfeeding rates or infant growth. Three studies reported improved weight gain in infants receiving hindmilk. Evidence on the effect of processing methods on morbidity and mortality was inconclusive. Limited evidence was found on freeze-thawing's efficacy in reducing CMV transmission, while pasteurization proved more effective. No studies assessed clinical outcomes related to hygiene practices or expression settings. The use of hindmilk improves infant weight gain with some certainty of evidence. Hand expression of MOM has similar efficacy on the growth of recipient infants to that of electric pumping, also for mothers of preterm infants. Evidence on clinical outcomes of different MOM expression practices and treatments is very limited. This work underscores the need for future studies to address the substantial evidence gaps identified. REGISTRY AND REGISTRY NUMBER FOR SYSTEMATIC REVIEWS OR META-ANALYSES: The study was registered on PROSPERO (CRD42024523299). Previous reviews have focused on the effects handling practices for expressed mother's own milk, such as expression methods, hygiene practices/settings during expressions, and storage and processing treatments on the composition of MOM; however, changes in composition do not necessarily correspond to changes in clinical outcomes. To our knowledge, this is the only systematic review to evaluate the effects of these practices on a large number of clinically relevant outcomes (growth, main morbidities, feeding tolerance, adverse events, viral and retroviral infections, other infections, nutrient deficiencies, neurodevelopment, and breastfeeding) of recipient infants. In this context, the present work is important to identify gaps in knowledge, including methodological limitations of existing evidence, and guide future research.