The association between congenital anomalies and autism spectrum disorders in a Finnish national birth cohort

Aim The first aim of this study was to evaluate the association between different subgroups of autism spectrum disorders (ASDs) (childhood autism, Asperger syndrome, and pervasive developmental disorder/pervasive developmental disorder – not otherwise specified [PDD/PDD-NOS]) and congenital anomalies. Second, we assessed the association among intellectually disabled children with ASDs in the subgroups of childhood autism and PDD/PDD-NOS. Method Nationwide population-based register data for children with a diagnosis of ASD (n=4449; 3548 males, 901 females) were collected during years 1987–2000 from the Finnish Hospital Discharge Register. Data on congenital anomalies were derived from the National Register of Congenital Malformations. Conditional logistic regression models were used as a statistical method. The association between ASD subgroups and congenital anomalies was stratified by the presence or absence of intellectual disability. Results Congenital anomalies occurred more frequently in all subgroups of ASD than in comparison participants (adjusted odds ratio [OR] for major congenital anomalies 1.8, 95% confidence interval [CI] 1.5–2.2, p<0.001). The association between congenital anomalies and childhood autism (OR 2.4, 95% CI 1.6–3.6, p<0.001) and between congenital anomalies and PDD/PDD-NOS (OR 3.7, 95% CI 2.4–5.7, p<0.001) among children with an intellectual disability was strong but remained significant also without intellectual disability (childhood autism: OR 1.7, 95% CI 1.3–2.3, p<0.001; PDD/PDD-NOS: OR 2.3, 95% CI 1.9–2.8, p<0.001). Interpretation The results suggest a significant association between ASDs and congenital anomalies regardless of the ASD subgroup. The association between childhood autism and PDD/PDD-NOS and congenital anomalies is stronger among children with intellectual disability is stronger than among those without intellectual disability. These results may have relevance in examining early risk factors in autism during fetal neurodevelopment.