Air pollution and cardiovascular events at labor and delivery: a case-crossover analysis

In this case-crossover study, we investigated the odds of having a labor/delivery with cardiovascular event (i.e., ischemic heart disease, stroke, heart failure, cardiac arrest/failure, and other or unspecified cardiovascular events) associated with acute exposure to common air pollutants.

We selected 680 women with singleton pregnancy and cardiovascular events at labor/delivery from 12 U.S. clinical sites (2002-2008). Exposures to six criteria air pollutants, six particulate constituents, and 26 air toxics were obtained using modified Community Multiscale Air Quality models. Conditional logistic regression models calculated the odds ratio (OR) and 95% confidence intervals (CI) comparing exposures during the day of delivery, the week before delivery, and each of the days of the week before delivery to two control periods before and after.

An interquartile range increase in particulate matter (PM) ≤2.5 microns and nitric oxide exposures during the week before delivery was associated with an 11% (OR 1.11, 95% CI: 1.01-1.23) and 21% (OR 1.21, 95% CI: 1.04-1.42) increased cardiovascular events odds, respectively. These pollutants, sulfur dioxide, carbon monoxide, PM ≤ 10 microns, and some PM constituents showed associations with event odds for days 0, 1, 5, and 6 before delivery. Inverse associations were observed for O₃ and some PM constituents as well as air toxics.

Cardiovascular events at labor/delivery merit more attention in relation to air pollution.