Living in an area with high levels of air pollution may increase a woman’s chance of miscarriage in the early stages of pregnancy, new research suggests.
The study, conducted by researchers in Beijing, analysed the records of more than 255,000 pregnant women, cross-referencing instances of missed miscarriage in the first trimester, plus levels of pollution where the women lived.
While the study uses the term “missed abortion in the first trimester (MAFT)”, in the UK, doctors tend to use the term “missed miscarriage”.
A missed miscarriage – also called a silent miscarriage – is when a woman experiences a miscarriage without knowing. Missed miscarriages are usually diagnosed during the 12-week scan. If the scan reveals the foetus has no heartbeat or that it hasn’t fully formed, a woman may be diagnosed as having had a missed miscarriage.
The authors looked at maternal exposure to four air pollutants: particle matter PM2.5, which largely comes from vehicle emissions; sulfur dioxide (SO2), produced during industrial manufacturing of materials that contain sulfur; ground-level ozone (O3), which is created when pollutants from sources like cars and industrial waste react chemically with sunlight; and carbon monoxide (CO), which is released when machinery and vehicles burn fossil fuels.
The study authors adjusted for factors such as sociodemographic characteristics, noting that areas of high pollution may also be poorer and more crowded, which could ultimately affect a pregnant woman’s health or the development of the foetus. But even considering these factors, they said, the risk of missed miscarriage in the first trimester “becomes more severe the higher the pollutant concentration”.
“The findings provide evidence linking foetus disease burden and maternal air pollution exposure,” they said in the study, published in the journal Nature Sustainability.
The authors did not directly test if pollution was the cause of miscarriage, but noted that more research is needed to investigate the apparent link.
In the meantime, the authors said that “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”.
Of course, that advice not feel particularly helpful to women unable to move home or who work in an area with high levels of pollution. Dr Matthew Loxham, an air pollution expert from the University of Southampton, previously told HuffPost UK that avoiding air pollution isn’t always possible.
There isn’t much evidence that face masks work, he said, although they might have a “very small effect”. Avoiding traffic could also help a little. “If you can steer clear of streets that are heavily trafficked, then you’re keeping away from emissions,” he explained.
If that’s not possible, said Dr Loxham, there is some evidence that walking on the side of the pavement furthest from the road can reduce your exposure. Walking, in general, is better than travelling inside a vehicle, because you’re less exposed to other pollutants from the car.
“The best thing is to keep on roads that are less busy,” he said.