OBJECTIVES: To determine the association between area and individual measures of social disadvantage and infant health in the United Kingdom (UK). DESIGN: Systematic review and meta-analyses. DATA SOURCES: 26 databases and web sites, reference lists, experts in the field and hand-searching. STUDY SELECTION: 36 prospective and retrospective observational studies with socio-economic data and health outcomes for infants in the UK, published from 1994 to May 2011. DATA EXTRACTION AND SYNTHESIS: Two independent reviewers assessed the methodological quality of the studies and abstracted data. Where possible, study outcomes were reported as odds ratios for the highest versus the lowest deprivation quintile. RESULTS: In relation to the highest versus lowest area deprivation quintiles the odds of adverse birth outcomes were 1.81 (1.71 to 1.92) for low birth weight, 1.67 (1.42 to 1.96) for premature birth and 1.54 (1.39 to 1.72) for still birth. For infant mortality rates the odds ratios were 1.72 (1.37 to 2.15) overall, 1.61 (1.08 to 2.39) for neonatal and 2.31 (2.03 to 2.64) for post-neonatal mortality. For lowest versus highest social class, the odds were 1.79 (1.71 to 1.92) for premature birth, 1.52 (1.44 to 1.61) for overall infant mortality, 1.42 (1.33 to1.51) for neonatal and 1.69 (1.53 to 1.87) for post-neonatal mortality. There are similar patterns for other infant health outcomes with the possible exception of failure to thrive, where there is no clear association. CONCLUSIONS: This review quantifies the influence of social disadvantage on infant outcomes in the UK. The magnitude of effect is similar across a range of area and individual deprivation measures and birth and mortality outcomes. Further research should explore the factors that are more proximal to mothers and infants, to help throw light on the most appropriate times to provide support and the form(s) that this support should take.