Air pollution data was obtained from air-monitoring stations for the study period. Using a geographic information system, exposure to air pollution during both the first trimester and the entire pregnancy was assessed for each woman according to her place of residence. They found that exposure to air pollutants throughout full-term pregnancies were associated with an increased risk of congenital malformations, with specific defects evident in the circulatory system and genital organs. They also discovered that exposure to air pollution was associated, although not significantly, with a higher risk of congenital defects.