Air pollution exposure can significantly decrease the chance of a live birth after IVF treatment, according to research that deepens concern about the health impacts of toxic air on fertility.
Pollutant exposure has previously been linked to increased miscarriage rates and preterm births, and microscopic soot particles have been shown to travel through the bloodstream into the ovaries and the placenta. The latest work suggests that the impact of pollution begins before conception by disrupting the development of eggs.
“We observed that the odds of having a baby after a frozen embryo transfer were more than a third lower for women who were exposed to the highest levels of particulate matter air pollution prior to egg collection, compared with those exposed to the lowest levels,” said Dr Sebastian Leathersich, a fertility specialist and gynaecologist from Perth who is due to present the findings on Monday at the European Society of Human Reproduction and Embryology annual meeting in Amsterdam.
Air pollution is one of the leading threats to human health and is estimated by the World Health Organization (WHO) to have caused 6.7 million deaths in 2019. Microscopic soot particles have been shown to cross from the lungs into the bloodstream and are transported to every organ in the body, raising the risk of heart disease, gastric cancers and dementia. The contamination has also being linked to reductions in intelligence.
“Pollution is harmful to almost all aspects of human health and it’s no surprise to me that reproductive health is also affected,” Leathersich said. “I’m hopeful that these findings will help to highlight the urgency of the situation – that climate change poses a serious and immediate threat to human reproductive health, even at so-called safe levels.”
The study analysed fertility treatments in Perth over an eight-year period, including 3,659 frozen embryo transfers from 1,836 patients, and tracked whether outcomes were linked to the levels of fine particulate matter, known as PM10. The overall live birthrate was about 28% per transfer. However, the success rates varied in line with exposure to pollutants in the two weeks leading up to egg collection. The odds of a live birth decreased by 38% when comparing the highest quartile of exposure to the lowest quartile.
“These findings suggest that pollution negatively affects the quality of the eggs, not just the early stages of pregnancy, which is a distinction that has not been previously reported,” Leathersich said.
The team now plan to study cells directly to understand why pollutants have a negative effect. Previous work has shown that the microscopic particles can damage DNA and cause inflammation in tissues.
Prof Jonathan Grigg, whose group at Queen Mary University of London uncovered evidence that air pollution particles are found in the placenta, said: “This study is biologically plausible since it has recently been discovered that inhaled fossil-fuel particles move out of the lung and lodge in organs around the body. Reproductive health can now be added to expanding list of the adverse effects of fossil fuel-derived particulate matter, and should prompt policymakers to continue to reduce traffic emissions.”
The link was apparent despite excellent overall air quality during the study period, with PM10 and PM2.5 levels exceeding WHO guidelines on just 0.4% and 4.5% of the study days, the scientists said. Australia is one of just seven countries that met the WHO’s guidelines in 2023, and this study is the latest to show evidence of harm even at relatively low levels of pollution.
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Prof Geeta Nargund, a senior NHS consultant and medical director of abc IVF and Create Fertility, said further work would be crucial to better understand the full impact of air pollution, which disproportionately affects those from lower socioeconomic backgrounds.
“In the face of a global fertility crisis, a clear picture of the link between environmental factors such as air pollution and fertility health or treatment outcomes could play an important part in tackling falling fertility rates,” she said.