Quantifying the Spectrum of Early Motor and Language Milestones in Sex Chromosome Trisomy.

BACKGROUND AND

OBJECTIVES

Sex chromosome trisomy (SCT) is a common chromosomal abnormality associated with increased risks for early developmental delays and neurodevelopmental disorders later in childhood. Our objective was to quantify the spectrum of early developmental milestones in SCT. We hypothesized later milestone achievement in SCT than the general population.

METHODS

Data were collected as part of the eXtraordinarY Babies Study, a prospective natural history of developmental and health trajectories in a prenatally identified sample of infants with SCT. Parent-reported, clinician-validated, early motor and language milestones were collected at ages 2, 6, 12, 18, 24, and 36 months. Age distributions of milestone achievement were compared with normative data.

RESULTS

In all SCT conditions, compared with normative data, there was increased variability and a later median age of skill development across multiple gross motor and expressive language milestones. Results also show a significant amount of overlap with the general pediatric population, suggesting that for many children with prenatally identified SCT, early milestones present within, or close to, the expected timeline.

CONCLUSIONS

As increasing numbers of infants with prenatal SCT diagnoses present at pediatric practices, we provide an evidence-based schedule of milestone achievement in SCT as a tool for pediatricians and families. Detailed data on SCT milestones can support clinical interpretation of milestone achievement. Increased variability and later median age of milestone acquisition in SCT compared with norms support consideration of all infants with SCT as high risk.