Behavioural problems in children who weigh 1000 g or less at birth in four countries

Background The increased survival chances of extremely low-birthweight (ELBW) infants (weighing ≤1000 g at birth) has led to concern about their behavioural outcome in childhood. In reports from several countries with different assessments at various ages, investigators have noted a higher frequency of behavioural problems in such infants, but cross-cultural comparisons are lacking. Our aim was to compare behavioural problems in ELBW children of similar ages from four countries. Methods We prospectively studied 408 ELBW children aged 8–10 years, whose parents completed the child behaviour checklist. The children came from the Netherlands, Germany, Canada, and USA. The checklist provides a total problem score consisting of eight narrow-band scales. Of these, two (aggressive and delinquent behaviour) give a broad-band externalising score, three (anxious, somatic, and withdrawn behaviour) give a broad-band internalising score, and three (social, thought, and attention problems) indicate difficulties fitting neither broad-band dimension. For each cohort we analysed scores in ELBW children and those in normal-birthweight controls (two cohorts) or national normative controls (two cohorts). Across countries, we assessed deviations of the ELBW children from normative or control groups. Findings ELBW children had higher total problem scores than normative or control children, but this increase was only significant in European countries. Narrow-band scores were raised only for the social, thought, and attention difficulty scales, which were 0·5–1·2 SD higher in ELBW children than in others. Except for the increase in internalising scores recorded for one cohort, ELBW children did not differ from normative or control children on internalising or externalising scales. Interpretation Despite cultural differences, types of behavioural problems seen in ELBW children were very similar in the four countries. This finding suggests that biological mechanisms contribute to behavioural problems of ELBW children.