Environment/Climate Change
Wildfire Smoke Exposure Increases Risk for Gestational Hypertension Samantha Piekos* Samantha Piekos Piekos Piekos Piekos University of Pennsylvania
Wildfire smoke exposure is a growing environmental threat, yet its effects on pregnancy remain poorly characterized. In a retrospective cohort study, we examined associations between wildfire smoke exposure and pregnancy complications among 287,612 singleton deliveries (2015–2020) across five western US states (CA, ID, MT, OR, and WA) through partnership with Providence St. Joseph Health. Daily wildfire-attributable PM₂.₅ exposure was estimated using the Childs et al. (2020) model mapped to residential census tracts. Smoke exposure was common (n=194,918; 67.8% of pregnancies). There was higher exposure among rural residents, middle socioeconomic and second-lowest area deprivation quintiles, younger individuals, those conceiving in the first half of the year, and non-Hispanic, Native American, Pacific Islander, or White populations (all p<0.0001 except Pacific Islander, p<0.05).
The primary outcomes were gestational hypertension, preeclampsia, and preterm birth. We identified 21 confounders using outcome-specific directed acyclic graphs and key predictors from an XGBoost model of smoke exposure (PR-AUC = 0.998), and we adjusted for these using propensity score matching. We identified gestational week susceptibility windows by comparing exposure levels between cases and controls. There was an increased risk of gestational hypertension during two periods: gestational weeks 3-7 (aOR=1.09, 95% CI: 1.03–1.15, p<0.01) and weeks 22-25 (aOR=1.07, 95% CI: 1.01–1.13, p<0.05). There was no difference in rates of preeclampsia or preterm birth in people exposed to smoke during these periods of pregnancy.
Smoke exposure during the early first or late second trimester increases the risk of gestational hypertension. Understanding this temporal vulnerability is essential for developing targeted public health interventions and mitigation strategies to protect pregnant people in wildfire-prone regions.