[Birth weight as a predictor of young men's intelligence. A historical cohort study]

The objective was to examine the relation between birth weight and cognitive function in young adult life. The study includes 4300 Danish conscripts born between 1973 and 1975, and the main outcome measure was the mean score in the Børge Prien IQ test at drafting. The score is the number of correct answers to 78 questions and it correlates with full scale intelligence quotient (IQ). Data on birth weight were collected from the birth registry. The mean score in the Børge Prien test increased from 39.9 at a birth weight of < or = 2500 g to 44.6 at a birth weight of 4200 g after adjustment for gestational age and length at birth, maternal age and parity, and other variables. Above a birth weight of 4200 the test score decreased slightly. Birth weight is associated with cognitive performance in young adult life and factors that interference with foetal growth may influence adult cognitive performance.