Air pollution linked to a decrease in IVF birth rate success, new study shows

Embargoed: 00:01 CEST, Monday, 8 July 2024

The study analysed PM₁₀ exposure in the two weeks leading up to oocyte collection, finding that the odds of a live birth decreased by 38% (OR 0.62, 95% CI 0.43-0.89, p=0.010) 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).

Conducted over an eight-year period in Perth, Australia, the research analysed 3,659 frozen embryo transfers from 1,836 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, 2 weeks, 4 weeks, and 3 months), with models created to account for co-exposures.

Increasing PM_2.5 exposure in the 3 months prior to oocyte retrieval was also associated with decreased odds of live birth, falling from 0.90 (95% CI 0.70-1.15) in the second quartile to 0.66 (95% CI 0.47-0.92) 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.

Dr Sebastian Leathersich, lead author of the study, explains, “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. We could therefore evaluate whether pollution was having an effect on the eggs themselves, or on the early stages of pregnancy.”

“Our results reveal a negative linear association between particulate matter exposure during the 2 weeks and 3 months prior to oocyte collection and subsequent live birth rates from those oocytes. 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.”

Ambient (outdoor) air pollution is one of the greatest environmental risks to health and is estimated to cause over 4 million premature deaths per year worldwide [2]. Exposure to fine particulate matter is associated with a range of adverse health conditions, including cardiovascular and respiratory diseases [3]. In 2021, 97% of the urban EU population was exposed to concentrations of PM_2.5 above the WHO annual guideline (5 µg (microgram) /m³) [4]. Although epidemiological data show a clear correlation between pollution and poorer reproductive outcomes, the mechanisms remain unclear [1].

Dr Leathersich furthers, “Climate change and pollution remain the greatest threats to human health, and human reproduction is not immune to this. 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.”

Professor Dr Anis Feki, Chair-Elect of ESHRE, comments, “This important study highlights a significant link between air pollution and lower IVF success rates, with a notable reduction in live births associated with higher particulate matter exposure before oocyte retrieval. These findings emphasise the need for ongoing attention to environmental factors in reproductive health.”

The study abstract will be published today in Human Reproduction, one of the world’s leading reproductive medicine journals.

ENDS

Notes to editors:

A reference to the ESHRE Annual Meeting must be included in all coverage and/or articles associated with this study.

For more information or to arrange an expert interview, please contact the ESHRE Press Office at: press@eshre.eu.

About the study author:

Dr Sebastian J Leathersich is a Fertility Specialist and Gynaecologist from Perth, Western Australia. He works at Fertility Specialists of Western Australia, part of City Fertility, and King Edward Memorial Hospital for Women in Subiaco, Australia. He is currently undertaking a PhD and a clinical Fellowship at Dexeus Fertility, Hospital Universitario Dexeus, Barcelona, Spain, and at the Universitat de Barcelona.

About the European Society of Human Reproduction and Embryology

The main aim of ESHRE is to promote interest in infertility care and to aim for a holistic understanding of reproductive biology and medicine.

ESHRE collaborates world-wide and advocates universal improvements in scientific research, encourages and evaluates new developments in the field, and fosters harmonisation in clinical practice. It also provides guidance to enhance effectiveness, safety and quality assurance in clinical and laboratory procedures, psychosocial care, and promotes ethical practice. ESHRE also fosters prevention of infertility and related educational programmes and promotes reproductive rights regardless of the individual’s background. ESHRE’s activities include teaching, training, professional accreditations, mentoring and career planning for junior professionals, as well as developing and maintaining data registries. It also facilitates and disseminates research in human reproduction and embryology to the general public, scientists, clinicians, allied personnel, and patient associations.

Website: https://www.eshre.eu/

About Human Reproduction

Human Reproduction is a monthly journal of ESHRE and is one of the top three journals in the world in the field of reproductive biology, obstetrics and gynaecology. It is published by Oxford Journals, a division of Oxford University Press.

References:

1. Leathersich S.J, et al (2024). Particulate matter (PM_2.5 and PM₁₀) exposure prior to oocyte collection is associated with decreased live birth rates in subsequent frozen embryo transfers. Human Reproduction.
2. World Health Organization. (2022). Ambient (outdoor) air quality and health. Retrieved from https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health
3. Health Organization. (2021). What are the WHO air quality guidelines? Retrieved from https://www.who.int/news-room/feature-stories/detail/what-are-the-who-air-quality-guidelines
4. European Environment Agency. (2023). Air pollution levels across Europe still note safe, especially for children. Retrieved from https://www.eea.europa.eu/en/newsroom/news/air-pollution-levels-across-europe#:~:text=EEA%20monitoring%20update%202022%3A%20air,particulate%20matter%20(PM2.5)