[Formula: see text] Caregiver-reported infant motor and imitation skills predict M-CHAT-R/F.

Altered motor and social-communicative abilities in infancy have been linked to later ASD diagnosis. Most diagnostic instruments for ASD cannot be utilized until 12 months, and the average child is diagnosed substantially later. Imitation combines motor and social-communicative skills and is commonly atypical in infants at risk for ASD. However, few measures have been developed to assess infant imitation clinically. One barrier to the diagnostic age gap of ASD is accessibility of screening and diagnostic services. Utilization of caregiver report to reliably screen for ASD mitigates such barriers and could aid in earlier detection. The present study developed and validated a caregiver-report measure of infant imitation at 4, 6, and 9 months and explored the relationship between caregiver-reported imitation and motor abilities with later ASD risk. Participants (N = 571) were caregivers of term and preterm infants recruited as part of a large multi-site study of PediaTrac™, a web-based tool for monitoring and tracking infant development. Caregivers completed online surveys and established questionnaires on a schedule corresponding to well-child visits from birth to 18 months, including the M-CHAT-R/F at 18 months. Distinct imitation factors were derived from PediaTrac at 4, 6, and 9 months via factor analysis. The results supported validity of the imitation factors via associations with measures of infant communication (CSBS; ASQ). Imitation and motor skills at 9 months predicted 18-month ASD risk over and above gestational age. Implications for assessment of infant imitation, detecting ASD risk in the first year, and contributing to access to care are discussed.