In preterm children, early-life mental trajectories aid to recognize those at risk of intellectual disability (intelligence quotient [IQ] <70) and borderline intelligence (IQ = 70–84), respectively, at school age for timely intervention.

• In a multicenter study in Taiwan, preterm infants born at <32 weeks’ gestation between 2001 and 2014 who underwent mental assessments (Bayley Scales of Infant Development) at corrected ages 6, 12, and 24 months and IQs at age 5.5 years were included.

• In participants (n=1,680 children), three mental trajectories were found: high-stable (59.7%), high-declining (35.3%), and low-declining (5.0%), in which the borderline-intelligence/intellectual-disability rate was estimated to be 14.1%/1.5%, 36.1%/13.7%, and 10.7%/82.1%, respectively.

• A 37.7-fold higher odds for intellectual disability and 4.4-fold higher odds for borderline intelligence were observed for the low-declining trajectory and the high-declining trajectory, respectively, vs children with normal intelligence.

• Models incorporating both risk factors and trajectory groups, vs models with risk factors alone (AIC [Akaike information criterion] 1,791.2), demonstrated superior overall performance (AIC 1,419.8) and increased prediction power for intelligence outcomes: low-declining trajectory for intellectual disability (AUROC [area under the receiver operating characteristic curve] increased from 0.81 to 0.92) and high-declining trajectory for borderline intelligence (AUROC increased from 0.68 to 0.75).