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Objective The incidence of attention deficit hyperactivity disorder (ADHD) and autism has increased in recent years. While there is a consensus that these are largely genetically driven conditions and the increase is primarily attributed to administrative changes, such as broader diagnostic criteria, prenatal factors, like maternal occupational exposure to chemicals, may also play some role. This study investigates the association between such exposures and the diagnosis of ADHD and autism in children.Material and Methods We used a nationwide Swedish register-based cohort covering births from 1994 to 2014. The dataset includes detailed maternal socioeconomic and demographic information and diagnoses made in children later in life. Maternal occupational exposures to 35 chemical agents were assessed from a job-exposure matrix linked to the self-reported occupation at the first prenatal visit (week 10). The study population was stratified by maternal work status during pregnancy (full-time or part-time, accounting for leave of absence). Data were analysed using logistic regression, reporting odds ratios (OR) and confidence intervals. Extensive sensitivity analyses were conducted to test the robustness of the results.Results In total, 608,862 children of full-time working mothers and 357,119 children of part-time working mothers were included. Preliminary results show an association between ADHD and exposure to gasoline engine exhaust (OR = 2.07 [1.40 – 3.06]), which remained robust across a series of sensitivity analyses (e.g., restriction to non-university educated mothers, first-time mothers). Other associations included exposure to carbon monoxide (OR = 1.45 [1.05 – 2.01]), iron (OR = 1.62 [1.03 – 2.56]), and paper and pulp dust (OR = 1.77 [1.01 – 3.09]).Conclusion This study provides evidence of an association between exposure to certain chemicals during pregnancy and autism or ADHD diagnoses in children. However, some associations were not robust in sensitivity analyses, and the genetic predispositions were not assessed. Further studies are needed to confirm these associations and clarify the underlying mechanisms.