4. Discussion
In this study, a registry-based population cohort was used to investigate associations between maternal exposure to ambient air pollution during weeks 3–8 of pregnancy and the risk of congenital heart defects in their offspring. The exposure assessment was based on a spatiotemporal modeling approach that enabled the calculation of weekly air pollutant levels throughout the Tel-Aviv region between 1999 and 2006. Increased exposure to PM10 was associated with an increased risk for multiple congenital heart defects, while increased exposure to PM2.5 was associated with a decreased risk for patent ductus arteriosus. For CO, O3, NO2 and SO2, no associations were found between gestational exposure during weeks 3–8 of pregnancy and the risk of any of the investigated congenital heart defect groups.