Associations between ambient air pollution and Hypertensive Disorders of Pregnancy

Background: Exposure to ambient air pollution is linked to adverse pregnancy outcomes. Previous reports examining the relationship between ambient air pollution and Hypertensive Disorders of Pregnancy have been inconsistent.

Objectives: We evaluated the effects of ambient air pollution on the odds of Hypertensive Disorder of Pregnancy and whether these associations varied by body mass index (BMI).

Methods: We conducted a retrospective, case-control study among 298 predominantly Hispanic women (136 clinically confirmed cases) who attended the Los Angeles County+University of Southern California Women's and Children's Hospital during 1996-2008. Trimester-specific carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), and particulate matter with aerodynamic diameter <10 μm and <2.5 μm (PM10, PM2.5) exposure were estimated based on 24-hour exposure level at residential address. Logistic regression models were fitted to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for two standard deviation increase in exposure levels.

Results: Exposures to CO and PM2.5 in the 1st trimester were significantly associated with Hypertensive Disorders of Pregnancy, and these associations were modified by BMI. In non-obese women (BMI <30), 1st trimester exposures to PM2.5 and CO were significantly associated with increased odds of Hypertensive Disorder of Pregnancy (ORs per 2-standard deviation increase in PM2.5 (7 μg/m(3)) and CO (1 ppm) exposures were 9.10 [95% CI: 3.33-24.6] and 4.96 [95% CI: 1.85-13.31], respectively). Additionally, there was a significantly positive association between exposure to O3 in the 2nd trimester and Hypertensive Disorder of Pregnancy (OR per 15 ppb=2.05; 95% CI: 1.22-3.46).

Conclusion: Among non-obese women, 1st trimester exposure to PM2.5 and carbon monoxide are associated with increased odds of Hypertensive Disorder of Pregnancy.