The Truth About Air Pollution & Miscarriages

One in four pregnant women in the UK experience a miscarriage, the loss of a pregnancy in the first trimester. It remains one of the most emotionally traumatising experiences a woman can go through, yet it's extremely common.

There are many reasons why a miscarriage occurs, but often the cause is never identified. According to the NHS, a miscarriage can be due to issues with the unborn baby, the development of the placenta or may be caused by underlying medical issues with the mother. Now questions have been raised about how the environment affects women during pregnancy.

A new study in China puts forward an alarming finding that women living in areas of high air pollution are 50% more likely to experience a miscarriage in their first trimester.

The study, which was published in the journal Nature Sustainability, analysed the records of 255,668 women living in Beijing between 2009 and 2017 and found that the 10 micrograms per cubic metre of toxic gas – sulphur dioxide and carbon monoxide from power plants and vehicle exhausts – increased the risk of miscarriage by 41% and further increase of the pollutant resulted in a 52% risk. 

The researchers 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, the lead author of the study, wrote 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."

Air pollution levels in China’s capital have fallen significantly in recent years, even as pollution readings differ dramatically from day to day and across parts of the city. But what does this mean for women living in the UK, where almost 2000 locations across England, Wales and Northern Ireland have levels of air pollution that exceed safety limits?

According to Dr Nicholas Raine-Fenning, a consultant gynaecologist and spokesperson for the Royal College of Obstetricians and Gynaecologists, women in the UK should not be alarmed but should take precaution.

"The Chinese data did not consider age, fertility or previous miscarriages and Beijing is a completely different environment. However, it would be absolutely wrong to ignore it and anything someone can do to limit their exposure to pollution is good advice," he told Refinery29. "For the vast majority, it won't have an impact and you can be reassured that you'll be fine, but the best advice is to be cautious and maximise all lifestyle changes. But should women wear face masks? No."

He adds that pregnant women should aim to eat a balanced diet and limit stress: "You should avoid smoking as this is a direct pollutant – and this includes vaping. I would avoid getting your hair and nails done and to stay as 'au naturel' as possible. This will limit your risk of putting chemicals in your body. Anxiety has also been proven to to have a direct impact on fertility, so it's important to limit stress and worry."

Nearly half of women who have miscarriages feel guilty and two in five feel it was caused by something they did wrong. Dr Raine-Fenning said women should stop blaming themselves.

The NHS usually investigates if a woman experiences three miscarriages. However, Dr Raine-Fenning cites other studies that suggest it's not unusual if a woman has up to four.

"So much of this is out of your control. Of course we don't want miscarriages to occur, but it's part of reproductive life. Miscarriages are commonly caused by abnormal genetics or immune issues and is something you're either born with or inherited," he said. "It's a very common process and there's nothing you've done wrong. You must not blame yourself."

Ruth Bender-Atik, the national director of the Miscarriage Association, agreed: "As with many unexpected and upsetting experiences, the question 'why did it happen?' is common after miscarriage. We look for explanation, both to explain what happened and in the hope of being able to prevent a recurrence.

"Without explanations, we tend to look inwards and assume it's something we did or didn't do. But it's truly rare for miscarriage to be caused by something that either partner can influence or cause, so while trying to stay healthy and follow pregnancy guidelines are both important, so too is accepting and really believing that miscarriage is not really anyone's fault."

Jane Brewin, chief executive of Tommy’s, a charity that funds research into miscarriage, stillbirth and pregnancy, said that while the study from China appeared to show a link between air pollution and miscarriages, it failed to recognise other factors. "This study appears to show a link between high levels of air pollution and miscarriage, which could be alarming for many pregnant women. However, we would read these results with caution as further investigations are needed." She adds that while the study focused on one of the most polluted cities in the world, it didn’t consider other factors, such as genetic abnormalities at the time of conception, which are more common. 

There are currently no national statistics that record the number of miscarriages in the UK. However, there is a legal requirement to record live births, still births and terminations, and these numbers are included in the UK population data. But there is no requirement to report on spontaneous pre-24-week pregnancy loss, including miscarriage, ectopic pregnancy or molar pregnancy (which is when a non-viable fertilised egg implants in the uterus and fails to come to term).

According to the NHS, if a miscarriage happens during the first trimester of pregnancy (the first three months) it’s usually caused by problems with the unborn baby. If a miscarriage happens after the first trimester, it may be the result of things like a mother's underlying health conditions, such as diabetes, lupus, kidney disease or infections, or if the mother smokes, uses drugs and/or alcohol. Late miscarriages may also be caused by an infection around the baby which leads to the waters breaking before any pain or bleeding. Miscarriages can also occur if there’s a problem with the development of the placenta. 

Last month, researchers in Belgium found toxic air particles in pregnant women’s placentas for the first time, raising concerns over the effects of air pollution on unborn foetuses. The study, which was led by Professor Tim Nawrot at Hasselt University, found that black carbon, a black sooty material which often comes from burning fossil fuels such as exhaust fumes from diesel engines, were found on the foetal side of the placenta – the closest side to the developing baby. The build-up was higher in women who lived in more polluted areas. This study points to a link between exposure to dirty air and increased miscarriages, premature births and low birth weights. The research suggested the particles themselves may be the cause, not solely the inflammatory response the pollution causes.

Black carbon is known to be harmful to human tissue and polluted air has been linked to various types of cancer and is known to damage the heart, brain, lungs and fertility. In pregnancy specifically, one expert said high blood pressure and even seizures have been linked to pollution in the air. 

"Various studies have described associations between prenatal ambient air pollution exposure and impaired birth outcomes," Dr Nawrot and his colleagues wrote in the journal Nature Communications at the time. "For instance, combustion-related particulate matter, including black carbon, is associated with lower birth rate, preterm birth, and intrauterine growth restriction."

Dr Karen Exley, group leader for air pollution at Public Health England, told Refinery29: "Poor air quality is the largest environmental risk to public health in the UK. Exposure during pregnancy may pose some specific risks, and there is growing evidence that air pollution is linked to low birth rate. The Committee on the Medical Effects of Air Pollutants is currently undertaking a review of the evidence regarding air pollution and effects on birth outcomes including miscarriage."

There’s no denying that the air quality in certain parts of the UK is abysmal. Each day we inhale smog, car exhaust fumes and secondhand cigarette smoke, as well as toxic particles that can harm our heart and lungs. An inquiry into the death of 9-year-old Ella Kiss Debrah last year found that it was caused by illegal levels of air pollution. Ella lived 25m (80ft) from London's South Circular Road in Lewisham, which was considered a notorious pollution "hotspot" at the time. She experienced three years of seizures and hospital stays for her asthma before her death in February 2013. During that time, local air pollution levels breached EU legal limits. The schoolgirl's death was the first to be linked to air pollution and forced the government to sit up and listen.

A spokesperson for the Department for Environment, Food and Rural Affairs said that the government is "stepping up the pace and taking urgent action to improve air quality" in the UK. 

"We are working hard to reduce transport emissions and are already investing £3.5 billion to clean up our air, while our Clean Air Strategy has been praised by the WHO as an example for the rest of the world to follow.

"Our Environment Bill will also drive further improvements for air quality, increasing local powers to address key sources of air pollution and introducing a duty to set a legally binding target to reduce fine particulate matter."

Earlier this week, the government confirmed its plans to introduce legally binding targets for air pollution. The pledge was included in the Queen’s Speech on Monday 14th October and will make up part of the long-awaited Environment Bill, which was one of 26 bills to be introduced in the speech.