DHA (22 : 6n-3) in pregnancy has previously been shown to benefit infant brain and retinal development. Fatty acid consumption during pregnancy may also have an impact on infant adipose tissue development. The objective of the present study was to assess the prenatal impact of a DHA-containing functional food (DHA-FF) on infant intra-uterine growth. This was a longitudinal, randomised, double-blinded, placebo-controlled trial. Pregnant women were assigned to consume a DHA-FF or placebo bar from 24 weeks' gestation until delivery. Blood samples were collected from mothers at baseline and delivery and from the umbilical cord at delivery. Plasma and erythrocyte fatty acids were analysed by GLC and plasma insulin concentrations were analysed using a commercially available ELISA kit. Infant birth weight and length were obtained at delivery and ponderal index (weight (g)/length (cm)3 × 100) was calculated. A total of forty-seven mothers completed the study. Infants of mothers consuming the DHA-FF during the last half of pregnancy had lower ponderal indices (β = 0·198, P < 0·05) and umbilical cord blood insulin concentrations (β = 0·743, P < 0·05) than infants of mothers consuming the placebo. Thus, DHA consumption during pregnancy may be advantageous with respect to infant body composition at birth and insulin sensitivity.