Birth weight and cognitive function in young adult life: historical cohort study

Abstract Objective: To examine the relation between birth weight and cognitive function in young adult life. Design: Retrospective cohort study based on birth registry data and cognitive function measured during evaluation for military service. Subjects: 4300 Danish conscripts born between 1973 and 1975. Main outcome measures: Mean score in the Boerge Prien test of cognitive function; score is the number of correct answers to 78 questions and correlates with full scale intelligence quotient (IQ). Results: Mean score in the Boerge Prien test increased from 39.9 at a birth weight of ≤2500 g to 44.6 at a birth weight of 4200 g even after adjustment for gestational age and length at birth, maternal age and parity, and other variables. Above a birth weight of 4200 g the test score decreased slightly. Conclusion: Birth weight is associated with cognitive performance in young adult life. Interference with fetal growth may influence adult cognitive performance. Key messages Low birth weight and proportionate smallness at birth have been associated with poorer cognitive function in early childhood Only a few studies have examined whether this association persists into adult life This study found that the mean cognitive test score in 4300 Danish conscripts increased up to a birth weight of 4200 g after adjustment for confounders; there was a slight decrease above a birth weight of 4200 g Fetal growth seems to influence adult cognitive performance If fetal growth has an impact on mental development it has important consequences from the perspective of maternal care