Exposures to air pollution and risk of acute-onset placental abruption: A case-crossover study

Background: Despite abruption's elusive etiology, knowledge of triggers that precede it by just a few days prior to delivery may help to understand the underpinnings of this acute obstetrical complication. We examine whether air pollution exposures immediately preceding delivery are associated with acute-onset abruptions. Methods: We applied a bidirectional, time-stratified, case-crossover design to births with an abruption diagnosis in New York City, 2008-2014. We measured ambient fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂). We fit distributed lag nonlinear models based on conditional logistic regression to evaluate individual exposure and cumulative exposures over lags 0-7 days before abruption, adjusted for temperature and relative humidity (similar lags to the main exposures). Results: We identified 1,190 abruption cases. We observed increased odds of abruption for exposure to PM_2.5 (per 10 μg/m³) on lag day 3 (odds ratio [OR] 1.19, 95% confidence interval [CI] = 0.98, 1.43), lag day 4 (OR 1.21, 95% CI = 1.01, 1.46), and lag day 5 (OR 1.17, 95% CI = 1.03, 1.33). Similarly, the odds of abruption increased with exposure to NO₂ (per 5 ppb) on lag day 3 (OR 1.16, 95% CI = 0.98, 1.37), lag day 4 (OR 1.19, 95% CI = 1.02, 1.39), and lag day 5 (OR 1.16, 95% CI = 1.05, 1.27). Exposures to PM_2.5 and NO₂ at other lags, or cumulative exposures, were not associated with abruption of acute onset. Conclusions: This case-crossover study showed evidence of an association between short-term ambient air pollution exposures and increased abruption risk of acute onset.