Birth defects remain a global health issue. With increasing rates of migration, it is important to explore the role of immigration and the impact of new environments, especially food fortification, on birth defect prevalence. The prevalence of birth defects in the first year of life was compared between children born to immigrant and non-immigrant mothers in Ontario, Canada. Data on country of origin and arrival date were identified for immigrant mothers. The rate of birth defects among mothers coming from some countries was higher than Canadian mothers including 12 to 27% higher rates among mothers arriving from Sudan, Jamaica, Bangladesh and Afghanistan. The rate of birth defects among immigrant mothers who arrived before food fortification in 2000 was higher than the rate in non-immigrants, but after 2000 it was lower among immigrant mothers. Comparing the birth defect rate among two cohorts at one point in time could be misleading. Higher rates of birth anomalies among immigrant mothers who arrived before food fortification could be due to lack of access to folic acid in their country of origin. After food fortification, immigrant mothers likely had similar exposure to folic acid as non-immigrant mothers and their rate of was the same or lower.