Incidence and risk factors for autism spectrum disorder among infants born <29 weeks' gestation

Objective This study was aimed to assess the incidence of and risk factors for autism spectrum disorder (ASD) among preterm infants born <29 weeks' gestational age (GA). Methods A retrospective cohort study of infants born <29 weeks' GA admitted to two tertiary neonatal intensive care units (2009 to 2017) and followed >= 18 months corrected age (CA) at a neonatal follow-up clinic. The primary outcome was ASD, diagnosed using standardized testing or provisional diagnosis at >= 18 months CA. Patient data and 18-month CA developmental outcomes were obtained from the local Canadian Neonatal Follow Up Network database and chart review. Stepwise logistic regression assessed factors associated with ASD. Results Among 300 eligible infants, 26 (8.7%) were diagnosed with confirmed and 21 (7.0%) with provisional ASD for a combined incidence of 15.7% (95% confidence interval [CI] 11.7 to 20.3). The mean follow-up duration was 3.9 +/- 1.4 years and the mean age of diagnosis was 3.7 +/- 1.5 years. Male sex (adjusted odds ratio [aOR] 4.63, 95% CI 2.12 to 10.10), small for gestational age status (aOR 3.03, 95% CI 1.02 to 9.01), maternal age >= 35 years at delivery (aOR 2.22, 95% CI 1.08 to 4.57) and smoking during pregnancy (aOR 5.67, 95% CI 1.86 to 17.29) were significantly associated with ASD. Among ASD infants with a complete 18-month CA developmental assessment, 46% (19/41) had no neurodevelopmental impairment (Bayley-III<70, deafness, blindness, or cerebral palsy). Conclusions ASD is common among infants born <29 weeks' GA and possibly associated with identified risk factors. Such findings emphasize the importance of ASD evaluation among infants <29 weeks' GA and for continued reporting of developmental outcomes beyond 18-months of corrected age.