Impaired motor and social skill development in infancy predict high autistic traits in toddlerhood.

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder. Early diagnosis in the critical period is important for ASD children. Recent studies of neurodevelopmental behavioral features and joint attention in high-risk infants showed there are some special cues which can distinguish ASD from typical development infant. But the findings of high-risk population may not be applicable to the general population. It is necessary to "analogically" study the potential warning traits of ASD in infancy in the general population. We did a nested case-control study from June 2019 to November 2022 in Tianjin, China, including 76 general infants whom completed the neurodevelopmental evaluation, the Checklist for Autism in Toddlers-23 (CHAT-23) screening, and eye tracking task. Social behavior quotient in infancy was negatively correlated to CHAT-23 total scores in toddlerhood. Social behavior quotient in infancy was positively correlated to initiating joint attention in toddlerhood. Regression model showed that high fine motor scale and social behaviour scale quotient in infancy were associated with an decreased risk of the total score of CHAT-23 ≥ 2 in toddlerhood. The Receiver operating characteristic curve showed the social behaviour in infancy alone and the combination of fine motor and social behaviour in infancy contributed to auxiliary diagnosis of higher level of autistic traits in toddlerhood. These findings suggest that Impaired development of fine motor and social behavior in infancy are potential warning features of high autistic traits in general population.