The cause of over 50 percent of recurrent miscarriages remains unidentified, often leaving couples in limbo about what may have caused it. However, new research from Imperial College London claims to have identified a hidden factor that may have been downplayed in decades of research.

The study, recently published in the journal Clinical Chemistry, argues that a male’s sperm quality might play a role in recurrent miscarriages, challenging the old assumption that the issue fundamentally lies in the female's health. 

Recurrent miscarriages affect up to 1 in 50 couples in the UK and are defined as over three consecutive pregnancy losses before 20-week's gestation. Typically, male partners are not screened since it was largely assumed to be caused by the female’s health issues, whether it be an infection or immune problems.

“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 analyzed,” Dr Channa Jayasena, lead author of the research from Imperial’s Department of Medicine, explained in a statement.

“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 fetus.”

By analyzing the sperm of 50 men whose partners had suffered from multiple miscarriages and 60 other men whose partners had not, the research team found a link between recurrent miscarriages and sperm health. The precise mechanism underlying this is still unclear, but it appears that the sperm of those who had suffered recurrent miscarriages had twice as much DNA damage than those who didn't.

Deeper analysis of the guys' sperm suggested that the cause of the DNA damage is most likely due to reactive oxygen species, oxygen-containing radicals formed by cells in the semen. While these molecules are used to protect sperm from infections, high concentrations can actually cause damage to sperm. Men whose partners had suffered multiple miscarriages had up to four times the amount of reactive oxygen species than the control group. 

Perhaps – although this is speculation at this point – the high levels of reactive oxygen species in the semen could be explained by previous infections, or bacteria lingering in the prostate gland, the researchers hypothesized. 

As ever, further research is needed to build on these findings, but the study already hopes to provide hope and optimism to couples battling with recurrent miscarriages. 

“It has taken medicine a long time to realize sperm health has a role to play in miscarriage – and that the cause doesn’t lie solely with women," Dr Jayasena said. "Now we realize 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.”