Fig 2.

Difference in standardised grade (z score) in written language and mathematics among children in the full sibling cohort (born in Denmark 1986-2003) by gestational age at birth compared with 40 gestational weeks, by adjustment, inclusion of those not taking examinations, and adjustment for potential mediators. For children not taking examinations, the 1% lowest centile standardised grade was imputed according to birth year. Potential mediators are prematurity associated morbidity and number of hospital admissions for children aged <16 years. Covariate adjusted only=adjustment for sex, relative birth weight, malformations, parental age, parental educational level, and number of older siblings. Covariate and sibling adjusted additionally includes adjustment for shared family factors. Analyses including children not taking examinations and those adjusted for potential mediators were adjusted for covariates and shared family factors