Ambient Air Pollution and Cardiovascular Malformations in Atlanta, Georgia, 1986–2003

A growing body of epidemiologic evidence suggests associations between ambient air pollution and adverse pregnancy outcomes (1–6). Associations between air pollution levels during pregnancy and risks of cardiovascular malformations among the offspring were investigated in 2 previous population-based case-control studies (7, 8). In these studies, cardiovascular malformations were classified by using preexisting surveillance database codes, and analyses were based on contrasts in ambient pollution levels over space and time. In the first study, conducted in southern California, investigators reported an association between ambient carbon monoxide levels and risk of ventricular septal defects (fourth quartile vs. first quartile, odds ratio = 2.95, 95% confidence interval (CI): 1.44, 6.05). Elevated risks of aortic artery and valve defects, pulmonary artery and valve defects, and conotruncal defects with increasing ambient ozone levels were also reported (7). The second investigation, conducted in Texas, did not corroborate the southern California findings, although a suggestive association between ozone and pulmonary artery and valve defects was observed. The Texas investigators reported positive associations for carbon monoxide and tetralogy of Fallot, particulate matter with an average aerodynamic diameter of <10 μm (PM10) and atrial septal defects, and sulfur dioxide and ventricular septal defects (8). We conducted a retrospective cohort study in Atlanta, Georgia, to explore temporal associations between ambient air pollution levels during pregnancy and risks of cardiovascular malformations. We did not closely replicate the methodologies of the previous studies. In addition to the retrospective cohort design and the temporal analytical approach, we reviewed and reclassified each surveillance record using a modified version of the International Pediatric and Congenital Cardiac Code implemented in the Society of Thoracic Surgeons Congenital Heart Surgery Database (9–13). This activity permitted classification of cardiovascular malformations according to embryologic (rather than only anatomic) considerations.