The use of pesticides has enhanced the health and economies of nations around the world by improving crop production. However, pesticides may pose health risks, particularly to the fetus and young children. In a secondary analysis of the Ontario Farm Family Health Study, we explored the relationship between birth defects and parental pesticide exposure during the 3 months prior to conception and the first trimester of pregnancy. A total of 3412 pregnancies were included in the study. Logistic regression fit by maximum likelihood was used in the analysis. The results showed that pre-conception exposure to both cyanazine (odds ratio=4.99, 95% confidence interval: 1.63-15.27) and dicamba (OR=2.42, 95% CI: 1.06-5.53) were associated with increased risk of birth defects in male offspring. Nevertheless, given the self-reported nature of the exposure and outcomes in this study, the present findings should be considered primarily as hypothesis generating, requiring verification in subsequent investigations.