Effects of Donor Human Milk and Formula Supplementation on Bone Metabolism and Clinical Outcomes in Preterm Infants Receiving Mother’s Own Milk

<b>Background:</b> Human milk (HM) is the optimal nutrition for preterm infants, but supplementation is often required to meet their unique nutritional needs. Donor human milk (DHM) and preterm formula are commonly used alternatives, yet their impacts on bone metabolism and clinical outcomes remain incompletely defined. <b>Objective:</b> To compare the effects of exclusive mother's own milk (MOM), MOM supplemented with DHM, and MOM supplemented with preterm formula on bone metabolism markers, growth milestones, and clinical outcomes in very preterm and very low birth weight (VLBW) infants. <b>Methods:</b> We conducted a retrospective review of medical records for infants born at <32 weeks' gestation or <1500 g birth weight between January 2018 and June 2023. Feeding groups included exclusive MOM (N = 135), MOM + DHM (N = 74), and MOM + Formula (N = 54). Biochemical markers were assessed at baseline and on days 7, 14, and 28. Multivariate regression analyses evaluated predictors of growth and clinical outcomes. <b>Results:</b> Infants in the MOM group had significantly lower gestational age and birth weight, with higher rates of respiratory morbidity. Time to full enteral feeding and duration of parenteral nutrition were longer in the MOM group, but feeding regimen was not an independent predictor of these outcomes. By day 14, the MOM group had higher alkaline phosphatase levels and lower phosphorus levels compared to mix feeding groups, but these differences resolved by day 28. Calcium levels varied between groups but remained within normal ranges. Necrotizing Enterocolitis (NEC) incidence did not differ significantly across feeding regimens and was primarily associated with longer parenteral nutrition duration. <b>Conclusions:</b> Supplementation of MOM with either DHM or preterm formula supported adequate growth and bone metabolism without increasing NEC risk. Feeding regimen did not independently influence time to full enteral feeding or length of hospitalization, which were driven primarily by infant maturity and clinical status. Both DHM and preterm formula are viable supplements to MOM, ensuring nutritional adequacy without adverse bone health effects. Prospective studies are needed to evaluate long-term outcomes of these feeding strategies.