An Irish scientist has discovered the cause of infertility in 80% of couples whose fertility problems are unexplained.

Currently in Ireland, up to one in three couples seeking help for fertility problems have unexplained, or idiopathic, fertility. This means that no detectable problem has been identified.

However, Prof Sheena Lewis of Queen's University in Belfast, has discovered that 80% of couples with unexplained infertility actually have a problem known as high sperm DNA damage.

According to Prof Lewis, many couples with infertility are given an explanation for their problems and once the causes have been established, 'the appropriate course of assisted conception treatment can be undertaken'.

However, for those with explained infertility, it can be unclear how to proceed.

"These couples often invest a lot of time and money in fertility treatments like intrauterine insemination (IUI), which are unlikely to be successful. In our study we have now had a breakthrough which explains the cause of infertility for many of those couples.

"Now that we have found the cause of infertility for these couples, suitable treatments can be tailored for them, which will direct them straight to the best treatment and increase their chances of having a baby," Prof Lewis explained.

She said that the research was possible due to the development of a unique test for male infertility, known as the SpermComet. This measures damaged DNA in individual sperm, which provides people with specific information about the causes and extent of their fertility problems.

"This test can predict the success of infertility treatments and fast-track couples to the treatment most likely to succeed, leading to reduced waiting times and improved chances of success.

"With one million couples worldwide requiring fertility treatment, these new research findings will give many fresh hope of having a family," Prof Lewis added.

Details of these findings are published in the journal, Reproductive Biomedicine Online.