Objective Early preterm infants (EP <32 weeks gestation) have an increased risk for developmental and behavioural disorders. Less is known on development of late preterm infants (LP, 32–36 weeks gestation). Objective of the study is to determine prevalence of developmental disorders in LP compared to EP and controls at age 4.

Methods In a community based prospective cohort study, parents of 965 LP, 561 EP, and 563 term infants (controls) born in 2002–2003 completed a developmental questionnaire at home, when the child was 43–51 months old. The Ages and Stages Questionnaire (ASQ) is a parent completed developmental screener that evaluates communication, gross motor, fine motor, problem solving and personal social developmental domains.

A test score less than the second centile of the results of the term infants was considered abnormal.

Results 16.5% of EP and 10.4% of LP had total scores below the cut off value, compared to 5.2% of the controls (χ² for trend p<0.001) After controlling for gender and maternal education, LP failed the ASQ more frequently than controls on communication (odds ratio (OR) 1.6, confidence interval (CI) 1.1 to 2.1), fine motor (OR 2.3, CI 1.4 to 3.8), personal-social (OR 1.6, CI 1.1 to 2.4) and total score (OR 1.9 CI; CI 1.3 to 3.0).

Conclusions The prevalence of developmental disorders as measured by the ASQ in late preterm infants is twice as high as in controls, and at least half as high as in early preterms. Domains most affected are fine motor, personal-social, communication and total score. This combination might well affect school performance.