Vaping could make women less fertile, experiments on mice have found.
E-cigarette vapour made it take longer for mice to get pregnant and their babies were less healthy and didn’t grow as quickly as those with clear lungs.
Marketed as safer than cigarettes and pushed by the UK health authorities as the best quitting aid, the popularity of vaping has soared in recent years.
But evidence is growing that all is not as it seems with smoke-free cigs,and studies show they can damage the lungs, blood vessels and heart – and now the reproductive system.
Michigan this week became the first US state to ban flavoured e-cigarettes amid health concerns as the country has launched an investigation into more than 200 cases of lung disease it thinks may be linked to the habit.
Researchers not involved with the study, however, said ‘humans are not mice’ and its results should be taken with a pinch of salt.
E-cigarettes are becoming increasingly popular in women who want to have children, researchers said, because they are believed to be significantly safer than tobacco (stock image)
In a lab study on mice researchers from the University of North Carolina found being exposed to the vapour from electronic cigarettes reduced female fertility.
They said the same findings could apply to people – mice are routinely used as pre-human test subjects because of biological similarities – and that male fertility also appeared to be affected.
It took three to four days longer for a fertilised embryo to become embedded in the womb if a mouse had been exposed to the vapour, meaning it was less likely to become pregnant.
And the baby mice were found to have damaged metabolisms and a higher risk of heart disease or diabetes because of their pre-birth exposure to the chemicals.
They also failed to gain as much weight as their smoke-free counterparts by eight-and-a-half months old – equivalent to middle-age in humans.
Study author Dr Kathleen Caron said: ‘We found e-cigarette usage prior to conception significantly delayed implantation of a fertilised embryo to the uterus – thus delaying and reducing fertility.
‘We also discovered e-cigarette usage throughout pregnancy changed the long-term health and metabolism of female offspring – imparting lifelong, second-generation effects on the growing foetus.’
She said the findings ‘change our views on the perceived safety of e-cigarettes’.
HOW COULD VAPING BE HARMFUL?
The flavourings in electronic cigarettes may damage blood vessels in the same way as heart disease, according to research published in June.
The chemicals used to give the vapour flavours, such as cinnamon, strawberry and banana, can cause inflammation in cells in the arteries, veins and heart.
They cause the body to react in a way that mimics the early signs of heart disease, heart attacks or strokes, the study by Boston University found.
Other recent studies have also suggested smoking e-cigarettes could cause DNA mutations which lead to cancer, and enable pneumonia-causing bacteria to stick to the lungs easier.
Researchers at New York University subjected human bladder and lung cells to e-cigarette vapor, which is marketed as being healthier than tobacco.
They found the cells mutated and became cancerous much faster than expected and mice exposed to the vapour also suffered significant DNA damage.
In another study, scientists at Queen Mary University, London, found vaping makes users more likely to catch pneumonia – just like smoking tobacco or breathing in traffic fumes.
The vapour from e-cigarettes helps bacteria which cause the condition to stick to the cells that line the airways, they said.
The effect occurs with traditional cigarette smoke and those who are exposed to air pollution high in particulates from vehicle exhausts.
Smoking tobacco is known to be extremely harmful to pregnant women and their unborn children and the NHS may refuse to give IVF to women who smoke.
At least 16 local NHS boards have also started to refuse fertility treatment to women who use e-cigarettes, over concerns about their health impacts.
But Dr Caron’s team found e-cigarette use was widespread among mothers-to-be because of claims it’s so much safer than smoking.
‘E-cigarette use is prevalent among pregnant women as a seemingly safe alternative to traditional tobacco use, which is known to result in foetal developmental abnormalities and impaired fertility of male offspring,’ Dr Caron said.
‘However, little is known about the effects of e-cigarette use on fertility or pregnancy outcomes.’
The mice in the study were exposed to clouds of e-cigarette vapour, which contains nicotine and chemicals including propylene glycol and vegetable glycerin, five times a week for four weeks before mating.
Another group were exposed to only normal air.
Dr Caron added: ‘After four months, e-cigarette exposed [mothers] exhibited a significant delay in the onset of the first litter.
‘Furthermore, exposure of new [mothers] during early pregnancy significantly impaired embryo implantation, as evidenced by near complete absence of implantation sites in e-cigarette exposed animals at day five despite exhibiting high levels of progesterone, an indicator of pregnancy.
‘Moreover, female offspring exposed to e-cigarettes in the womb exhibited a significant weight reduction at 8.5 months, while males exhibited a slight, but non-significant, deficiency in fertility.
‘Thus, e-cigarette exposure in mice impairs pregnancy initiation and foetal health, suggesting that e-cigarette use in reproductive-aged women or during pregnancy should be considered with caution.’
However, other scientists were more reluctant to link the study to advice for people.
Professor Ying Cheong, from the University of Southampton, said: ‘We expect that e-cigarettes are “safer” than normal cigarettes as promoted, but this study provides early evidence that e-cigarettes may be harmful to fertility in mice.
‘But humans are not mice, and we will need much more evidence to claim the detrimental impact to fertility in humans.
‘As quitting cigarette smoking is a challenge for many, if e-cigarettes use help people quit, they should not be put off by this news as the benefits are likely still to be significant.’
The University of Edinburgh’s Professor Linda Bauld added: ‘This study is in mice, and if we used mouse models to guide all advice to pregnant women there would be very few medications we could allow them to use and many more products they would need to avoid.
‘While it is preferable that pregnant women quit smoking and use no nicotine products in pregnancy, in practice this is very difficult for some women and therefore alternatives are needed.’
E-cigarettes have also been linked to damage in the blood vessels similar to that cause by heart disease.
A study by Boston University last year found chemicals in the vapour flavourings could cause swelling in cells in the arteries, veins and heart.
And recent work by the American Heart Association suggested people who vape may be at a 71 per cent higher risk of stroke and a 59 per cent higher risk of heart attack.
Dr Caron’s research was published in the Journal of the Endocrine Society.