We examined the relation between place of birth and cognitive function in young adult life in a historical cohort study based upon birth data from the computerized Danish Medical Birth Registry and cognitive function as measured at time of drafting for military service in two Danish counties. The cohort included 4,296 Danish conscripts born between 1973 and 1976, 123 born at home and 4,173 born in hospital or at a birth clinic, Cognitive function was measured by the Boerge Prien test in men, 18 to 20 years of age. The highest possible score is 78. The mean Boerge Prien test score was 43.1 for conscripts born in specialized hospital departments, 2.4 higher for conscripts born in a birth clinic (95% confidence interval = 0.9-4.0), and 2.1 Lower for conscripts born at home (95% confidence limits = -3.8 to -0.4) after adjusting for birth weight, length at birth, birth order, gestational age, maternal age, and marital and occupational status. Our findings raise the possibility that home birth can lead to lower cognitive function in adulthood; however, from our data we could not distinguish between planned and unplanned births at home.
