5. Summary and conclusion
This work contributes to the small body of knowledge regard- ing the association between congenital heart defects and in-utero exposure to air pollution. A spatiotemporal methodology of weekly inverse distance weighting in registry-based birth cohort was used and a 10 μg/m3 increase in PM10 exposure was associated with a 5% increase in the risk for multiple congenital heart defects. The inverse associations regarding maternal exposure to PM2.5 and isolated patent ductus arteriosus cases need further investigation.