Children born extremely preterm show significant lower cognitive, language and motor function levels compared with children born at term, as measured by the Bayley-III at 2.5 years.

AIM To assess developmental outcomes of children aged 2.5 years born extremely preterm. METHODS As a part of the population-based Extremely Preterm Infants in Sweden Study (EXPRESS), 399 children born before 27 weeks of gestation and 366 control children born at term were assessed with the Bayley Scales of Infant and Toddler Development, third edition (Bayley-III), assigning scores for cognition, receptive and expressive communication, fine and gross motor functions. Based on control group means, prevalences of developmental delay in the preterm group were calculated. Mean score differences between subtests constituting the overall Bayley-III indices were analysed within both groups. RESULTS After controlling for socio-demographic, child and assessment variables, analyses showed significantly lower performances of the preterm group compared with the control group on the Bayley-III subtests. Prevalence of moderate-severe delay was 10.8% in cognitive, 14.9% in receptive communication, 14.5% in expressive communication, 12.4% in fine motor and 7.0% in gross motor functions. Significant differences between performances on subtests included in the same indices were detected. CONCLUSION Extremely preterm children show significant lower cognitive, communicative and motor function levels at 2.5 years compared with children born at term. Bayley-III assessments permit the acquisition of nuanced information about development following extreme prematurity.