July 21, 2024

Exposure to air pollution can significantly reduce the chance of a live birth after IVF treatment, according to research that deepens concerns about the health impact of toxic air on fertility.

Pollution exposure has previously been linked to increased miscarriage rates and premature births, and microscopic soot particles have been shown to travel through the bloodstream to the ovaries and the placenta. The latest work suggests that the impact of pollution begins before fertilization by disrupting the development of eggs.

“We noticed that the chance of having a baby after a frozen embryo transfer was more than a third lower for women exposed to the highest levels of particulate air pollution before egg collection, compared to those exposed to the lowest levels were exposed,” said Dr Sebastian Leathersich, a fertility specialist and gynecologist from Perth who will present the findings at the annual meeting of the European Society of Human Reproduction and Embryology in Amsterdam on Monday.

Air pollution is one of the biggest threats to human health and is estimated by the World Health Organization (WHO) caused 6.7 million deaths in 2019. Microscopic soot particles have been shown to pass from the lungs into the bloodstream and be transported to every organ in the body, increasing the risk heart disease, stomach cancer and dementia. The pollution is also 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 am hopeful that these findings will help 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 analyzed fertility treatments in Perth over an eight-year period, including 3,659 frozen embryo transfers from 1,836 patients, and looked at whether outcomes were linked to levels of fine particulate matter, known as PM10. The overall live birth rate was approximately 28% per transfer. However, the success rates varied according to pollutant exposure in the two weeks leading up to egg collection. The chance 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 not previously reported,” Leathersich said.

The team now plans 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 of air pollution particles being found in the placenta, said: “This study is biologically plausible as it has recently been discovered that inhaled fossil fuel particles travel out of the lung and lodge in organs around the body. Reproductive health can now be added to the expanding list of adverse effects of fossil fuel-derived particulates, and should prompt policymakers to continue to reduce traffic emissions.”

The link was evident 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 only seven countries which met WHO 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 will be crucial to better understand the full impact of air pollution, which disproportionately affects those from lower socioeconomic backgrounds.

“In light of a global fertility crisis, a clear picture of the relationship between environmental factors such as air pollution and fertility health or treatment outcomes could play an important role in tackling declining fertility rates,” she said.

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