Importance Perinatal infections are commonly present in preterm and very low-birth-weight (VLWB) infants and might contribute to adverse neurodevelopmental outcome. OBJECTIVE To summarize studies evaluating the effect of perinatal infections on neurodevelopmental outcome in very preterm/VLBW infants. EVIDENCE REVIEW On December 12, 2011, we searched Medline, PsycINFO, Embase, andWeb of Knowledge for studies on infections and neurodevelopmental outcome. All titles and abstracts were assessed for eligibility by 2 independent reviewers.We also screened the reference lists of identified articles to search for additional eligible studies. Preselected criteria justified inclusion in this meta-analysis: (1) the study included infants born very preterm (≤32 weeks) and/or with VLBW (≤1500 g); (2) the study compared infants with and without perinatal infection; (3) there was follow-up using the Bayley Scales of Infant Development 2nd edition; and (4) results were published in an English-language peer-reviewed journal. The quality of each included study was assessed using the Newcastle-Ottawa Scale. FINDINGS This meta-analysis includes 18 studies encompassing data on 13.755 very preterm/VLBW infants. Very preterm/VLBW infants with perinatal infections had poorer mental (d=-0.25; P < .001) and motor (d =-0.37; P < .001) development compared with very preterm/VLBW infants without infections. Mental development was most impaired by necrotizing enterocolitis (d=-0.40; P < .001) and meningitis (d=-0.37; P < .001). Motor development was most impaired by necrotizing enterocolitis (d=-0.66; P < .001). Chorioamnionitis did not affect mental (d=-0.05; P = .37) or motor (d= 0.19; P = .08) development. CONCLUSIONS AND RELEVANCE Postnatal infections have detrimental effects on mental and motor development in very preterm/VLBW infants.