Sperm with damaged DNA could trigger recurrent miscarriages

Recurrent miscarriages may be the fault of MEN, scientists claim as they link them to poor sperm with DNA damage

  • Imperial College London scientists say men’s health is important to pregnancy
  • Sperm with damaged DNA could make a pregnancy less likely to succeed
  • And the damage could be caused by high levels of oxygen reactive species
  • These molecules are protective for sperm but toxic in high concentrations  

Sperm could be to blame in the cases of women who have recurrent miscarriages, a study has suggested.

Although doctors generally look to the mother for the cause of a miscarriage, scientists think the father’s health could play an important role, too.

The sperm of men whose partners have three or more miscarriages tend to have more DNA damage, which could be triggering the failed pregnancies.

Experts say working out why men’s sperm are becoming damaged, and whether that is triggering miscarriages, could lead the way to new fertility treatments.

They suggest past infections or STIs, obesity, or being older could trigger higher levels of DNA-damaging molecules.

Imperial College London scientists say their research could provide evidence fathers and the health of their sperm have an important role in women having successful pregnancies

Research by Imperial College London found the partners of women who suffered recurrent miscarriages have twice as much DNA damage as the average man.

And they have four times higher levels of oxygen reactive species, common but potentially damaging molecules which the scientists suggest could corrupt DNA.

‘Traditionally doctors have focused attention on women when looking for the causes of recurrent miscarriage,’ said lead researcher Dr Channa Jayasena.

‘The men’s health – and the health of their sperm, wasn’t analysed.

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‘However, this research adds to a growing body of evidence that suggests sperm health dictates the health of a pregnancy.

‘For instance, previous research suggests sperm has an important role in the formation of the placenta, which is crucial for oxygen and nutrient supply to the foetus.’

Recurrent miscarriages – the loss of three or more pregnancies before 20 weeks – affect around one in 50 couples in the UK.


It is more common for a woman to have a miscarriage than a baby, according to a study published last year.

Experts say it is wrong to think of a miscarriage as a rare mistake, because it’s actually more common than a successful pregnancy but many happen so early they go unnoticed. 

This, says the scientist who wrote the study, is because of deadly genetic abnormalities in eggs which stop them ever developing into babies. 

The experience can be very upsetting for hopeful parents but even women in their 20s have about a 50/50 chance of a fertilised egg becoming a baby, the University of California researchers claimed.

And the rate rises as women get older, with those in their late 40s having an average of more than 30 miscarriages per live baby.

Campaigners say it would be helpful for people to have more education about how common miscarriage is, so people understand it is ‘the norm’. 

Infection or immune problems in the mother have traditionally been viewed as possible causes.

But Imperial’s small study of 110 male volunteers revealed significant differences in the sperm of men whose partners suffered miscarriages and those whose didn’t.

The oxygen reactive species, of which the miscarriage-affected men have more, protect sperm from bacteria and infection but can be harmful in high concentrations.

Researchers now want to work out what affects men’s levels of these molecules, suggesting it could be a history of STIs, obesity or age.

Dr Jayasena said: ‘Although none of the men in the trial had any ongoing infection such as chlamydia – which we know can affect sperm health – it is possible there may be other bacteria from previous infections lingering in the prostate gland, which makes semen.

‘This may lead to permanently high levels of reactive oxygen species.’

He also explained high levels of body fat are also believed to trigger an increase in the molecules, and researchers found men in the miscarriage group were heavier.

Dr Jayasena added: ‘Although this is a small study, it gives us clues to follow.

‘If we confirm that high levels of reactive oxygen species in semen increase the risk of miscarriage we could try to develop treatments that lower these levels and increase the chance of a healthy pregnancy.

‘It has taken medicine a long time to realise sperm health has a role to play in miscarriage – and that the cause doesn’t lie solely with women.

‘Now we realise both partners contribute to recurrent miscarriage, we can hopefully get a clearer picture of the problem and start to look for ways of ensuring more pregnancies result in a healthy baby.’ 

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