Eriksen, Hanne-Lise Falgreen4; Kesmodel, Ulrik Schiøler5; Underbjerg, Mette6; Kilburn, Tina Røndrup7; Bertrand, Jacquelyn7; Mortensen, Erik Lykke8
1 Section of Occupational and Environmental Health, Department of Public Health, Faculty of Health and Medical Sciences, Københavns Universitet2 Department of Public Health, Faculty of Health and Medical Sciences, Københavns Universitet3 Center for Healthy Ageing, Faculty of Health and Medical Sciences, Københavns Universitet4 Institut for Klinisk Medicin - Center for Funktionelt Integrativ Neurovidenskab5 Institut for Klinisk Medicin - Gynækologisk/Obstetrisk afd. Y- SKS6 Klinisk Epidemiologisk Afdeling7 unknown8 Section of Occupational and Environmental Health, Department of Public Health, Faculty of Health and Medical Sciences, Københavns Universitet
family, pregnancy and birth characteristics, postnatal influences, and postnatal growth
Parental education and maternal intelligence are well-known predictors of child IQ. However, the literature regarding other factors that may contribute to individual differences in IQ is inconclusive. The aim of this study was to examine the contribution of a number of variables whose predictive status remain unclarified, in a sample of basically healthy children with a low rate of pre- and postnatal complications. 1,782 5-year-old children sampled from the Danish National Birth Cohort (2003-2007) were assessed with a short form of the Wechsler Preschool and Primary Scale of Intelligence - Revised. Information on parental characteristics, pregnancy and birth factors, postnatal influences, and postnatal growth was collected during pregnancy and at follow-up. A model including study design variables and child's sex explained 7% of the variance in IQ, while parental education and maternal IQ increased the explained variance to 24%. Other predictors were parity, maternal BMI, birth weight, breastfeeding, and the child's head circumference and height at follow-up. These variables, however, only increased the explained variance to 29%. The results suggest that parental education and maternal IQ are major predictors of IQ and should be included routinely in studies of cognitive development. Obstetrical and postnatal factors also predict IQ, but their contribution may be of comparatively limited magnitude.