Individual differences in cognitive ability may in part have prenatal origins. In high-risk (low birth weight/premature) babies, birth weight correlates positively with cognitive test scores in childhood, but it is unclear whether this holds for those with birth weights in the normal range. The authors systematically reviewed literature on the relationship between normal birth weight (more than 2,500 g) and childhood intelligence in term (37-42-week gestation) deliveries. Six studies met the inclusion criteria, and the authors present a comprehensive narrative review of these studies. There was a small, consistent, positive association between birth weight and childhood cognitive ability, even when corrected for confounders. Parental social class accounted for a larger proportion of the variance than birth weight, and these 2 variables were largely independent.