The relative effect of size at birth, postnatal growth and social factors on cognitive function in late childhood

To investigate if fetal, head, and somatic postnatal growth are independent predictors of cognition and estimate their relative importance compared to the effect size of social factors on cognitive function at 10 years.

Longitudinal population-based data from the birth questionnaire and the 5- and 10-year sweeps of the 1970 British Birth Cohort Study were used, including 11,244 subjects. Multiple linear regression and structural equation modeling were used in the statistical analysis. Standardized coefficients were used to measure and compare effect sizes.

Fetal growth, head, and somatic postnatal growth were significant independent predictors of cognition at age 10. These associations remained even among children born within the normal birth-weight range and those who did not experience neonatal problems. Effect of head size on cognition was greater than the effect of birth weight. Weight at 10 had a small negative effect on cognition. Gestational age was not directly associated with cognitive function, but it had a weak indirect effect. Parent's socioeconomic status was strongly associated with child's cognitive function.

Although effect sizes of prenatal and postnatal growth on cognition are modest compared with the strong effect size of social factors, they might have greater impact at the population level, since most children are born without low birth weight.