Acute effects of air pollutants on spontaneous pregnancy loss: a case-crossover study

Objective To investigate the relationship between acute exposure to air pollutants and spontaneous pregnancy loss. Design Case-crossover study from 2007 to 2015. Setting An academic emergency department in the Wasatch Front area of Utah. Patient(s) A total of 1,398 women who experienced spontaneous pregnancy loss events. Intervention(s) None. Main Outcome Measure(s) Odds of spontaneous pregnancy loss. Result(s) We found that a 10-ppb increase in 7-day average levels of nitrogen dioxide was associated with a 16% increase in the odds of spontaneous pregnancy loss (odds ratio [OR] = 1.16; 95% confidence interval [CI] 1.01–1.33; P =.04). A 10-μg/m 3 increase in 3-day and 7-day averages of fine particulate matter were associated with increased risk of spontaneous pregnancy loss, but the associations did not reach statistical significance (OR 3-day average = 1.09; 95% CI 0.99–1.20; P =.05) (OR 7-day average = 1.11; 95% CI 0.99–1.24; P =.06). We found no evidence of increased risk for any other metrics of nitrogen dioxide or fine particulate matter or any metric for ozone. Conclusions We found that short-term exposure to elevated levels of air pollutants was associated with higher risk for spontaneous pregnancy loss.