Language, motor and cognitive development of extremely preterm children: Modeling individual growth trajectories over the first three years of life

Survival rate of extremely low gestational age (ELGA) newborns has increased over 80% in the last 15 years, but its consequences on the short- and longer-term developmental competencies may be severe. The aim of this study was to describe growth trajectories of linguistic, motor and cognitive skills among ELGA children, compared to full-term (FT) peers, from the first to the third year of life, a crucial period for development. Growth curve analysis was used to examine individual and group differences in terms of initial status at 12 months and rate of growth through the second and the third year of life with five points of assessment. Twenty-eight monolingual Italian children, of whom 17 were ELGA (mean GA 25.7 weeks) and 11 were FT children, were assessed through the BSID-III at 12, 18, 24, 30 and 36 months for language skills and at 12, 24 and 30 months for motor and cognitive skills. ELGA children presented significantly lower scores than FT peers in language, motor and cognitive skills and they did not overcome their disadvantage by 3 years, even if their corrected age was taken into account. Concerning growth curves, in motor development a significant increasing divergence was found showing a Matthew effect with the preterm sample falling further behind the FT sample. In linguistic and cognitive development, instead, a stable gap between the two samples was found. In addition, great inter-individual differences in rate of change were observed for language development in both samples. Our findings highlight the theoretical and clinical relevance of analyzing, through growth curve analyses, the developmental trajectories of ELGA children in language skills taking into account their inter-individual variability also across motor and cognitive domains. Learning outcomes: After reading this article, the reader will interpret: (a) characteristics and growth trajectories of ELGA children from the first to the third year of life with respect to FT children in language, motor and cognitive development; (b) the method of growth curve analyses to describe group as well as inter-individual trajectories; (c) the rate of inter-individual variability in language as well as motor and cognitive skills, which gives useful indications for early interventions.