Children born preterm are at high risk for autism spectrum disorder (ASD). However, there is still a lack of appropriate developmental markers.

 In this study, we aim to examine whether early mental performance trajectory is related to ASD outcome in the preterm population.

The population-based cohort included 414 very preterm survivors born between 2008 and 2014.

 After excluding children with severe neurosensory impairment, 319 children with available records of developmental quotients before age 2 years were enrolled.

 The trajectory of mental performance evaluated by using the Bayley Scales of Infant Development across 6, 12, and 24 months of age was analyzed with group-based trajectory modeling.

 At 5 years of age, the ASD diagnosis was established by using the Autism Diagnostic Observation Schedule and the Autism Diagnostic Interview–Revised.