Air pollution exposure during pregnancy and preterm birth in Brazil

Ambient air pollution is a significant environmental risk factor for adverse pregnancy outcomes, including preterm birth. However, the impact of different pollutants across various regions and trimesters of pregnancy has not been fully investigated in Brazil. This study aimed to examine the associations between exposure to PM_2.5, NO₂, and O₃ during different trimesters of pregnancy and the risk of preterm birth across five regions of Brazil. We used logistic regression models to estimate the odds ratios (OR) of preterm birth associated with PM_2.5, NO₂, and O₃ adjusting for potential confounders such as maternal age, education, and socioeconomic status. Our study included over 9.9 million live births from 2001 to 2018, with data obtained from the Ministry of Health in Brazil. On average, for each 1-μg/m³ increase in PM_2.5, we estimated a 0.26 % (95 % CI: 0.08-0.44 %) increase in the risk of preterm birth nationally in the first trimester. For NO₂, each 1ppb increase was associated with a percentage increase in preterm birth risk of 7.26 % (95 % CI: 4.77-9.74 %) in the first trimester, 8.05 % (95 % CI: 5.73-10.38 %) in the second trimester, and 7.48 % (95 % CI: 5.25-9.72 %) in the third trimester. For O₃, each 1ppb increase was associated with a percentage increase in preterm birth risk of 1.24 % (95 % CI: 0.29-2.18 %) in the first trimester, 1.51 % (95 % CI: 0.60-2.41 %) in the second trimester, and 0.72 % (95 % CI: -0.18-1.62 %) in the third trimester. This study highlights the significant impact of ambient air pollution on preterm birth risk in Brazil, with significant regional variations. Our findings underscore the need for targeted public health interventions to mitigate the effects of air pollution on pregnancy outcomes, particularly in the most affected regions.