Men should undergo tests when couples suffer repeated miscarriages, according to researchers who say the health of the man’s sperm may sometimes be a factor.

The focus is usually on the woman’s body when multiple pregnancies fail, with tests usually looking for immune system problems or infection. But a small government-funded study by scientists at Imperial College London suggests miscarriage could also be a result of male issues, particularly if they are not routinely tested.

“Traditionally, doctors have focused attention on women when looking for the causes of recurrent miscarriage. The men’s health – and the health of their sperm – wasn’t analysed,” said Dr Channa Jayasena, the lead author of the research, from Imperial’s department of medicine.

“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.”

The team tested 50 men whose partners had suffered recurrent miscarriages, defined as the loss of three consecutive pregnancies before 20 weeks’ gestation. All were patients at St Mary’s hospital, in London. The scientists analysed their sperm and compared the results with those of 60 similar male volunteers.

The sperm of the men in the miscarriage group had twice as much DNA damage as that in the control group, they found. The researchers, writing in the journal Clinical Chemistry, say this could be down to reactive oxygen species – molecules formed by cells in semen to protect sperm from bacteria and infection. In high enough concentrations, the molecules can cause significant damage to sperm cells.

The results from the study revealed sperm from men whose partners had suffered miscarriage had four times more of these molecules compared to the control group. The scientists are now investigating the cause.

“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,” said Jayasena.

Obesity can also cause fertility problems. Higher fat levels in the body could trigger an increase in reactive oxygen species.

The men whose partners had suffered miscarriage were older than the other group, with an average age of 37 compared to 30, and were slightly more overweight. The team is now investigating whether these factors may have affected the levels of reactive oxygen species.

Dr Kevin McEleny of the British Fertility Society said: “This is an interesting study that illustrates the importance of research into sperm quality. The results agree with some of the previous research into a link between DNA damage in sperm and miscarriage.

“We know that the partners of older men are more likely to suffer miscarriage. The study group was generally older than the control group, which might go some way to explain the results.

“The study picked up small differences in hormone levels; it is not clear if these findings are of clinical relevance, because the average hormone levels of all groups were well within normal range. Minor differences in sperm quality were observed but the significance of that isn’t clear.”

Jayasena concluded: “Although this is a small study, it gives us clues to follow. If we confirm in further work 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.”