Longitudinal trends in maternal child-directed speech addressed to children with sex chromosome trisomies.

Children with Sex Chromosome Trisomies (SCTs) face a risk for developmental language vulnerabilities. Understanding how the Child-Directed Speech (CDS) adapts to these developmental trajectories is crucial for early intervention. This longitudinal study mapped the evolution of CDS addressed to 16 children with SCTs from 8 to 24 months of age. Results revealed significant changes. Structurally, the input transitioned in line with typical development, showing significant increases in lexical variety and syntactic complexity. Functionally, mothers transitioned from a more affective/attention-getting speech to a higher proportion of informative utterances. Prosodically, features associated with attention-driven communication decreased by 24 months. These findings suggest that the changes in CDS are driven primarily by the child's emerging communicative competence, rather than being constrained by the genetic diagnosis. The study highlights the responsiveness of CDS and its role as a protective factor that must be supported to facilitate optimal language development in this at-risk population.