Air pollution can raise the risk of a miscarriage by more than 50 percent, according to new research.

A study of more than a quarter of a million pregnant women found living on a busy road was more dangerous to the health of their baby than smoking.

There was a direct link between levels of toxic chemicals from the burning of fossil fuels and the number of cases of ‘missed’ – also known as ‘silent’ – miscarriage’.

These included tiny particles called PM2.5s, sulphur dioxide, ozone and carbon monoxide that are belched into the atmosphere by transport and industry.

Pregnant women living and working in big cities were advised to protect themselves and their unborn babies – by wearing masks, for example.

It would also help boost the population of ageing societies across the world – including the UK’s.

Lead author Professor Liqiang Zhang, of Beijing Normal University, said: “We find the risk is associated with rises for all four pollutants – and increases with higher concentrations.”

For instance, a hike of 10 micrograms per cubic metre in sulphur dioxide (S02) from power plants and vehicle exhausts made mums-to-be up to 41 percent more prone.

And above this the risk soared an extra 52 percent – further identifying the connection.

Prof Zhang said: “This means the risk increase is not linear but becomes more severe the higher the pollutant concentration.

“The findings provide evidence linking foetus disease burden and maternal air pollution exposure.”

Last month a Belgian team detected black soot in the placentas of all the women they studied – after they gave birth.

It followed mounting concerns that air pollution is causing premature births and low birth weights.

The latest study published in Nature Sustainability is based on the clinical records of 255,668 women in Beijing who gave birth between 2009 and 2017.

The area has a severe miscarriage crisis and is notorious as one of the most polluted cities in the world.

Among the participants 17,497 (6.8%) experienced a ‘missed miscarriage’ in the first three months – where the body doesn’t recognise the foetus has died.

These incidents were compared with exposure to the pollutants based on measurements from air monitoring stations near their homes and work places.

Prof Zhang said toxic chemicals could pass through the placenta and attack the immune system of a developing foetus.

He said: “Our findings 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.

“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.

“China is an ageing society and our study provides an additional motivation for the country to reduce ambient air pollution for the sake of enhancing the birth rate.

“Although ambient air pollution has reduced in China in recent years, pollution levels are still high and must reduce further for many reasons, including reducing missed miscarriage.”

Further research is needed to understand the specific mechanism by which air pollution affects the foetus, he said.

Prof Zhang said: “Poor air quality is a leading cause of global disease burden.

“Considerable evidence has consistently indicated that maternal exposure to air pollution contributes to increased risks of adverse birth outcomes such as low birthweight, preterm birth, gestational hypertension and pre-eclampsia – and may also affect maternal health during pregnancy and over the course of a woman’s life.”

Almost three-in-ten expectant women are at risk of losing their baby in developed countries – with missed miscarriage occurring in up to one-in-seven pregnancies.

Prof Zhang said: “Determining whether or not the risk responds to air quality conditions is important as a pregnancy loss is devastating for the parents.”

It’s not known how air pollution harms a foetus but scientists believe it can cause inflammation and other problems in the womb.

In 2016 a report by the Royal College of Physicians and the Royal College of Paediatrics and Child Health said toxins emitted by diesel cars were fuelling a health crisis that kills 40,000 Britons a year.

Smog from busy roads and toxins from industrial emissions were linked to premature births, stillbirth, miscarriage, low birth weight and organ damage, it found.

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