Adaptive Skill Trajectories in Infants with Fragile X Syndrome Contrasted to Typical Controls and Infants at High Risk for Autism.

•Infants with fragile X syndrome show adaptive skills deficits across all domains by 9 months of age.•Trajectories of these skills are delayed, albeit growing, before the age of 2.•Elevated autism symptomatology impairs adaptive skill growth in infants with fragile X syndrome.•All domains of adaptive skills should be targeted for intervention in infants with fragile X.