Men's exposure to ambient air pollution and in vitro fertilization outcomes among an infertility treatment population.

While men's exposure to air pollution is associated with decrements in semen quality, downstream impacts on pregnancy remain under-explored. This is particularly important for in vitro fertilization (IVF), associated with high costs and treatment burden among couples experiencing infertility. We examined men's ambient air pollution exposure and IVF treatment outcomes in the Folic Acid and Zinc Supplementation Trial (2013-2018, n = 238 with at least one IVF cycle from Salt Lake City region). Daily residential fine particulate matter (PM2.5), nitrogen dioxide (NO2), ozone (O3), and sulfur dioxide were abstracted from the Community Multiscale Air Quality model and averaged across spermatogenesis and susceptible windows of mitosis, meiosis I-II, spermiogenesis, and spermiation timed to date of the semen sample provided during IVF treatment cycles (n = 234 cycles with fresh embryos and n = 280 cycles with fresh or frozen embryo transfer). Treatment-cycle embryo outcomes and probability of pregnancy, pregnancy loss, and live birth were assessed using generalized linear mixed models adjusted for age, season, income, and co-pollutants. Overall, we did not identify a clear impact of air pollutants on probability of pregnancy, pregnancy loss, or livebirth. However, higher air pollution was associated with lower proportion of good quality day 3 embryos (e.g. mean difference (MD): 7.8%, 95% CI -15.1, -0.4% for NO2 and MD -5.3%, 95% CI -9.8, -0.7% for O3 per 5 ppb during meiosis I + II) and lower fertilization rate. While findings suggest a potential impact of men's exposure to air pollution on embryo development, we did not observe downstream impacts on IVF pregnancy outcomes.