Urban air pollution and in vitro fertilization outcomes: A Canadian retrospective study

There is growing data to support an adverse relationship between air pollution and fertility. Many studies have shown that traffic-related air pollution, the most common source of urban air pollution in North America, has a negative effect on both spontaneous and IVF pregnancy outcomes. This single-center retrospective study is the first Canadian study to explore urban air pollution exposures and IVF/ICSI outcomes. It included autologous IVF/ICSI outcomes from both fresh (ET - n = 1756) and frozen embryo transfer (FET - n = 1535) cycles between 2000 and 2022. Air pollution data for fine particulate matter (PM2.5) and nitrogen dioxide (NO₂) were obtained from The Canadian Urban Environmental Health Research Consortium (CANUE). Data was analyzed using bivariate maps of long-term air pollutant exposure (PM2.5 and NO₂) and IVF/ICSI clinical outcomes by 5 km² urban areas. We found that long-term air pollution within patients' household area ranged from 4.8 to 12.6 μg/m³ for PM2.5 and 3.2-28 ppb for NO₂. Nitrogen dioxide has demonstrated an association to some IVF/ICSI outcomes, which agrees with other international studies. No statistical associations in IVF/ICSI outcomes were found after adjusting for confounding variables. Understanding of the impact of urban air pollution on fertility and IVF/ICSI outcomes warrants further research on interventions to ameliorate negative outcomes and supports policy change(s) to improve air quality in the future.