Researchers from Beijing, China carried out an investigation to explore whether a link could be found between air pollution and miscarriage.
Published in the journal Nature Sustainability, the team analysed the records of more than a quarter of a million pregnant women living in the Chinese capital between 2009 and 2017.
The researchers contrasted the women’s records with their exposure to air pollutants, including sulphur dioxide and carbon monoxide.
The scientists concluded that the presence of 10 micrograms per cubic metre of sulphur dioxide in the air, from power plants and vehicle exhausts, increased risk of miscarriage by 41 per cent.
A further increase of the air pollutant resulted in a 52 per cent risk of miscarriage, according to the study.
The researchers also found a direct link between the levels of toxic chemicals in the air from the burning of fossil fuels and the number of cases of “missed miscarriages”, which occur when a woman who has experienced a miscarriage does not immediately exhibit symptoms.
Professor Liqiang Zhang, of Beijing Normal University and lead author of the study, said the findings of the research “uncovered potential opportunities to prevent or reduce harmful pregnancy outcomes by proactive measures before pregnancy”.
“Meanwhile, our study helped us understand the relationship between air pollution exposure and a spectrum of reproductive outcomes,” Professor Zhang stated.
“Pregnant women or those who want to become pregnant must protect themselves from air pollution exposure not only for their own health but also for the health of their foetuses.”
Professor Zhang added that further research is needed to understand exactly how air pollution affects a foetus in the womb.
Dr Patrick O’Brien, consultant obstetrician and spokesperson for the Royal College of Obstetricians and Gynaecologists (RCOG), said the study “adds to an ever-growing body of evidence on the association between air pollution and an adverse impact on babies’ health, even before they are born”.
“This study explores the risk associated with a silent, or missed miscarriage, in the first trimester – overall, 6.8 per cent of women experienced this, and they were more likely to do so if they lived in more polluted areas,” Dr O’Brien said.
“Exposure to some level of air pollution is unavoidable in day-to-day life and more research is required in this area on the impact to foetal development.”
Dr O’Brien added that the RCOG advises that pregnant women “seek to minimise their exposure to air pollution” where possible, and make lifestyle changes such as quitting smoking.
Ruth Bender-Atik, national director of the Miscarriage Association, said that other factors, such as poverty and poor diet, need to be taken into account when evaluating how air pollution affects pregnant women.
“You might expect these in polluted inner-city areas and it would be interesting and important to see if there was the same impact (on miscarriage rate) amongst higher groups in those areas (if they exist),” Ms Bender-Atik said.
“Nevertheless, the advice to pregnant women in polluted areas to wear masks makes sense, though of course the research would still need to be done to see if that makes a significant difference.”
Ms Bender-Atik added that those who live in polluted areas who are disadvantaged economically “have little option to make other lifestyle changes, such as moving to less polluted areas”.
A study published in September found that black carbon particles had been found on the foetal side of the placenta in women who were exposed to air pollution during pregnancy.