BackgroundThe inhibition of gastric acid secretion with ranitidine is frequently prescribed off-label to newborns admitted to neonatal intensive care units (NICU). Some studies show that the use of inhibitors of gastric acid secretion (IGAS) may predispose to infections and necrotising enterocolitis (NEC), but there are few data to confirm this association. This study aimed to compare the rates of neonatal infections and NEC among preterm infants (<37 weeks gestation) hospitalised in a NICU exposed or not to treatment with ranitidine.MethodsA retrospective cohort study was conducted with all consecutive preterm newborns admitted to a NICU between August-2014 and October-2015. The rates of infection, NEC, and death of newborns exposed or not to ranitidine were recorded.ResultsA total of 300 newborns were enrolled, of which 115 had received ranitidine and 185 had not. The two groups were similar with regard to the main demographic and clinical characteristics. Forty-eight (41.7%) of the 115 infants exposed to ranitidine and 49 (26.5%) of the 185 infants not exposed were infected (RR = 1.6, 95%CI 1.1–2.2, p = 0.006). The late onset (>48 h) blood culture positive infection rate was higher in the group exposed to ranitidine than in the untreated group (13.0% vs. 3.8%, p = 0.001). There was no significant association between the use of ranitidine and NEC (Bell stage >II) (p = 0.36). The mortality rate risk was 4-fold higher in infants receiving ranitidine (16.5% vs. 8.6%, p < 0.001).ConclusionRanitidine use in neonates was associated with an increased risk of infections and mortality, but not with NEC.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-017-2482-x) contains supplementary material, which is available to authorized users.