Air pollution and fecundability in two preconception cohort studies

Abstract

BACKGROUND AND AIM: Increasingly, epidemiologic studies have indicated an association between air pollution and reduced fertility. However, most studies have been conducted in small, selected populations, among couples receiving fertility treatment, or have used residential distance to roadways as a proxy for air pollution exposure. In this symposium presentation, we will review the literature on air pollution and fertility, and present new results from two preconception cohort studies based on improved exposure estimation. METHODS: We conducted parallel analyses in two internet-based cohorts in North America (Pregnancy Study Online [PRESTO], n=3,812) and Denmark (Snart Gravid/Snart Foraeldre [SG/SF], n=10,183). Eligible women were aged 18-45 years and attempting to conceive without fertility treatment. Participants completed a baseline questionnaire on socio-demographic, medical, reproductive, and behavioral factors. They were followed every two months until pregnancy or up to twelve months. We geocoded time-varying residential addresses from the year before baseline until conception or censoring. In PRESTO, we used spatio-temporal models to estimate monthly concentrations of NO2, O3 and PM2.5 (2013-2017), and in SG/SF monthly concentrations of NO2, NOx, CO, O3, SO2, PM2.5 and PM10 (2007-2019). We used proportional probabilities models to compute fecundability ratios (FR) and 95% confidence intervals (CI), adjusting for potential individual- and neighborhood-level confounders and co-pollutants. RESULTS:Preliminary analyses in PRESTO suggested a slight reduction in fecundability at higher average annual PM2.5 concentrations (≥10 vs. 6 µg/m3: FR=0.87, 95% CI: 0.70-1.07) with little evidence of a linear association; analyses of NO2 and O3 are ongoing. In SG/SF, PM2.5 concentrations were also associated with slightly reduced fecundability (≥13.0 vs. 8.0 µg/m3: FR=0.84, 95% CI: 0.62-1.14); other pollutants were not appreciably associated with fecundability. CONCLUSIONS:Higher estimated exposure to PM2.5 was associated with slightly lower fecundability in North American and Danish cohorts, after controlling for multiple potential confounders and other pollutants. KEYWORDS: air pollution, PM 2.5, fecundability, fertility, preconception cohort