Growth Efficiency of Donor Human Milk Compared With Maternal Milk and Formula in Preterm Infants

Importance Human milk is beneficial for preterm newborns, and pasteurized donor human milk (PDHM) is increasingly used when mother’s own milk (MM) is insufficient. However, PDHM has been associated with suboptimal growth outcomes. Objective To quantify the comparative clinical effectiveness of PDHM, MM, and formula in supporting daily weight gain and growth outcomes during the birth hospitalization. Design Retrospective cohort study of infants born before 34 weeks’ gestation between 2016 and 2024 Setting Five newborn nurseries across the Mass General Brigham healthcare system (Boston, MA), including one Level IV, one Level III, and three Level II newborn units. Participants A total of 2,635 preterm infants born before 34 weeks’ gestation between 2016 and late 2024 were included in the daily weight gain analysis, contributing 40,007 days of eligible enteral intake data for evaluation of in-hospital growth outcomes. For the analysis examining the association between PDHM use and discharge weight, 2,719 infants met eligibility criteria. Exposures PDHM, MM, formula Main Outcomes and Measures The primary outcome was daily weight gain (g/kg/day). The secondary outcome was the change in weight Z-score from birth to discharge. Results In adjusted analyses, an equal volume of PDHM was associated with 74% of the daily weight gain achieved with MM (p 2500 preterm infants contributing over 40,000 infant-days of enteral data, PDHM correlated with significantly reduced daily weight gain compared with MM, whereas formula supported greater weight gain than either human milk source. At discharge, infants with the highest quartile of PDHM exposure showed a greater reduction in weight-for-age Z-score than infants with no PDHM exposure. No association was observed in the lower quartiles. Meaning Our findings underscore the need for close growth monitoring and potentially greater nutritional supplementation in relation to PDHM exposure.