Variability and pathways in longitudinal trajectories of early gross motor development in healthy, term born infants.

Abstract

Aim: With the importance of repeated measurements versus on-time measurement becoming more distinct, insight in longitudinal early gross motor development in typically developing infants is needed. This study explored and described longitudinal gross motor development in healthy, term born infants measured every two months from the age of 3.5 till 12.5 months. Primary objectives were: explore and describe intra and interindividual variability and explore gross motor development and identify groups of individuals with common pathways. Methods: This study was a prospective longitudinal observational pilot, part of the study Gross mOtor Development of Infants using home-Video registration with the Alberta Infant Motor Scale following infants over time. Intra- and interindividual variability of gross motor development was visually explored and described using z-scores and cut-off below -1 standard deviation (SD). Longitudinal individual raw scores, general linear model and fitting a regression function were used to identify common pathways. Results: The final pilot cohort consist of 72 healthy infants, term born with a gestational age of 39.8(±1.3) weeks and a birthweight of 3512(±385) grams. Difference in z-scores over time varied between 4.07 and 0.02 with 61.1% of the infants showing z-scores below -1SD at some point and 40.3% more than once. Two groups of individuals with common pathways were identified through visual exploration and confirmed by repeated measurement ANOVA and curve estimation. These pathways represent early developers (n=32) and late bloomers (n=40). Conclusion: Findings of this study suggest gross motor development shows intra- and intervariability with different rate in emergence of gross motor abilities in Dutch healthy typically developing individuals. These findings support the premise that single-time measurements might not be fit for assessment of gross motor development at early ages. Gross motor development is distinguished by two different pathways identifying early developers and late bloomers. Clinical Relevance: These findings underline the importance of longitudinal screening for gross motor development in order to achieve adequate assumptions and practice. Professionals should realise divergent scores might still be a component of typical development and room for spontaneous increase should be motivated.