Background: To determine whether the introduction of pasteurized donor human milk and probiotics for infants born < 32 weeks gestational age or < 1500 g birthweight is associated with a reduction in mortality and the incidence of necrotising enterocolitis (NEC) and sepsis.

Methods: We performed a retrospective analysis of two cohorts: before and after the introduction of probiotics and pasteurized donor human milk. Univariate analysis of primary and secondary outcomes was performed; variables impacting outcomes were assessed using multivariate logistic regression.

Results: There were 1791 infants: 1334 in the pre-donor milk/probiotic cohort and 457 in the post-donor milk/probiotic cohort. On univariate analysis, mortality (7.6 vs. 2.4%, P < 0.001) and incidence of sepsis (6.2 vs. 3.5%, P = 0.028) were statistically significantly lower in the post-donor milk/probiotic group. NEC (2.8 vs. 1.5%, P = 0.14) and non-NEC associated gastrointestinal perforation (1.6 vs. 0.4%, P = 0.052) were lower in the post-donor milk/probiotics cohort, but these were not statistically significant. The difference in mortality remained statistically significant on multivariate analysis in the post-donor milk/probiotic cohort compared to those in the pre-donor milk/probiotic cohort (odds ratio 0.31, 95% confidence interval 0.16-0.61). The decrease in the incidence of NEC was consistent with previous observational studies but the difference was not statistically significant.