Background Ambient air pollution has been implicated in the development of hypertensive disorders of pregnancy (HDP). However, evidence of the association between air pollution and HDP is still limited, and the effects of gaseous air pollutants on HDP and their time windows of exposure have not been well studied.

Methods We used the Florida birth registry data to investigate the associations between air pollutants (NO₂, SO₂, PM_2.5, O₃ and CO) and the risks of HDP in 22 041 pregnant women in Jacksonville, Florida, USA from 2004 to 2005. Further, we examined whether air pollution exposure during different time windows defined by trimesters and the entire pregnancy had different effects on HDP.

Results The single-pollutant logistic regression model showed that exposure to four pollutants during the full pregnancy period was significantly associated with prevalence of HDP after adjusting for covariates: NO₂ (OR=1.21, 95% CI 1.09 to 1.35), PM_2.5 (OR=1.24, 95% CI 1.08 to 1.43), SO₂ (OR=1.13, 95% CI 1.01 to 1.25) and CO (OR=1.12, 95% CI 1.03 to 1.22) per IQR increase. Similar effects were observed when first trimester exposure to NO₂, SO₂ and CO, and second trimester exposures to PM_2.5 were examined. Consistent results were confirmed in multiple-pollutant models.

Conclusions This study suggests that exposure to high levels of air pollution during early pregnancy and the full gestational period was associated with increased prevalence of HDP in Florida, USA.