Air pollution linked to decrease in IVF birth rate success

Exposure to fine particulate matter (PM) prior to the retrieval of oocytes (eggs) during in vitro fertilisation (IVF) can reduce the odds of achieving a live birth by almost 40%, according to a new study presented at the ESHRE 40th Annual Meeting and published in the journal Human Reproduction.

Conducted over an eight-year period in Perth, Western Australia, the research analysed 3659 frozen embryo transfers from 1836 patients. The median female age was 34.5 years at the time of oocyte retrieval and 36.1 years at the time of frozen embryo transfer. The study examined air pollutant concentrations over four exposure periods prior to oocyte retrieval (24 hours, two weeks, four weeks and three months), with models created to account for co-exposures.

“This is the first study that has used frozen embryo transfer cycles to separately analyse the effects of pollutant exposure during the development of eggs and around the time of embryo transfer and early pregnancy,” said lead author Dr Sebastian Leathersich, from the King Edward Memorial Hospital for Women. “We could therefore evaluate whether pollution was having an effect on the eggs themselves, or on the early stages of pregnancy.”

Analysing PM₁₀ exposure in the two weeks leading up to oocyte collection, the researchers found that the odds of a live birth decreased by 38% when comparing the highest quartile of exposure (18.63 to 35.42 µg/m³) to the lowest quartile (7.08 to 12.92 µg/m³). Increasing PM_2.5 exposure in the three months prior to oocyte retrieval was also associated with decreased odds of live birth, falling from 0.90 in the second quartile to 0.66 in the fourth quartile.

Importantly, the negative impact of air pollution was observed despite excellent overall air quality during the study period, with PM₁₀ and PM_2.5 levels exceeding WHO guidelines on just 0.4% and 4.5% of the study days, respectively.

“Our results reveal a negative linear association between particulate matter exposure during the two weeks and three months prior to oocyte collection and subsequent live birth rates from those oocytes,” Leathersich said. “This association is independent of the air quality at the time of frozen embryo transfer. 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.”

Exposure to fine particulate matter through outdoor air pollution is already associated with a range of adverse health conditions, including cardiovascular and respiratory diseases. In 2021, 97% of the urban EU population was exposed to concentrations of PM_2.5 above the WHO annual guideline of 5 µg/m³. But although epidemiological data show a clear correlation between pollution and poorer reproductive outcomes, the exact mechanisms remain unclear

“Climate change and pollution remain the greatest threats to human health, and human reproduction is not immune to this,” Leathersich said. “Even in a part of the world with exceptional air quality, where very few days exceed the internationally accepted upper limits for pollution, there is a strong negative correlation between the amount of air pollution and the live birth rate in frozen embryo transfer cycles. Minimising pollutant exposure must be a key public health priority.”

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