Objective: This study examined a national cohort of 2.5-year-old children born extremely preterm with respect to behavioral problems from the perspective of parents and whether developmental variables mediated the effects of extreme prematurity on behavioral problems.

Methods: As a part of the Extremely Preterm Infants in Sweden Study (EXPRESS), 344 children born before 27 weeks of gestation and 338 control children were given the Cognitive, Language, and Motor Scales of the Bayley-III and the Parent report Child Behavior Checklist/1½-5 (CBCL/1½-5). CBCL/1½-5 assigns 7 syndrome scores, further classified into composite scores for internalizing and externalizing behavior as well as total problems. Group differences in behavioral difficulties and prevalence of clinical problems were calculated. Bayley-III scores were used in regression models to determine if developmental factors mediated the effects of extreme prematurity on behavioral problems, after controlling for sociodemographic factors.

Results: Preterm children had significantly higher mean T-scores on internalizing, externalizing, and total problems, as compared with the control subjects, but these were still within the average range. However, the proportion of subjects showing behavioral problems within the clinical range was significantly higher in the preterm group. Levels of cognitive, language, and motor development mediated the between-group differences in behavioral problems.

Conclusion: Our findings encourage behavioral assessments during preschool years and emphasize the importance of considering multifactorial pathways of prediction when examining prematurity outcome.