Environment/Climate Change
Wildfire smoke and fetal loss in California Dana Goin* Dana Goin Marianthi-Anna Kioumourtzoglou Tarik Benmarhnia Rachel Morello-Frosch Michael Leung Amy Padula
Background: Wildfires in California have been increasing in number and severity over the last several decades, and there is mounting evidence that they adversely affect reproductive health. However, there is a gap in the literature about the relationship between wildfire smoke and fetal loss.
Objective: To evaluate the effect of increased wildfire smoke during pregnancy on the rate of fetal loss using live birth-identified conceptions (LBIC).
Methods: We used California birth records from 2017-2019 and linked pregnancies to Census places using geocoded addresses. We estimated the week of conception for each birth and calculated the weekly count of LBICs for each Census place. We then linked this cohort of LBICs (identified by each Census place and week) to wildfire particulate matter (PM2.5) data for 40 weeks of pregnancy. We used a quasi-Poisson regression model with distributed lag terms to estimate the rate ratio of LBICs. We also estimated the fetal loss count difference (CD) using G-computation with nonparametric bootstrap for inference. We included weekly non-wildfire PM2.5 and temperature as confounders.
Results: For a given week of pregnancy, wildfire PM2.5 had a right-skewed distribution with a mean (SD) of 5.2 (33.2) μg/m3. Approximately 30% of the Census place-weeks had non-zero wildfire PM2.5 levels. We observed a reduction in livebirths and thus an increase in fetal loss associated with higher wildfire PM2.5 exposure. We identified three gestational periods for which associations were the strongest: weeks 1-3, 26-28, and 37-40 of pregnancy. We observed the largest effect estimates during gestational week 1 (RR=0.996, 95% CI 0.992, 1.000 ;and CD = 0.15, 95% CI 0.11, 0.22) and week 40 (RR = 0.995, 95% CI 0.991, 0.999; and CD=0.20, 95% CI 0.13, 0.31) associated with a 5 μg/m3 increase in wildfire PM2.5.
Conclusions: Wildfire smoke exposure, especially during gestational weeks 1-3, 26-28, and 37-40, is associated with an increased risk for fetal loss.