New research shows high levels of sperm DNA damage could be behind 80% of "unexplained infertility" issues.


Currently, 50,000 couples in the UK require fertility treatment and up to a third are diagnosed with "unexplained infertility", having undergone inconclusive tests that show no conceivable problem with the woman and seemingly no problem with the man’s semen.

However, according to new research conducted by Queen’s University Belfast, 80% of these cases are due to detectable sperm DNA damage in the man.

Lead researcher Professor Sheena Lewis told us, “Of those 80% of men who have sperm DNA damage, 40% have a lot of damage. IVF is less likely to work for these couples, compared to those who have a normal amount of sperm DNA damage (less than 15%).”

Sheena explains, “Sperm is a cell which only has one job, to combine its DNA with the DNA of a woman’s egg to make a baby. So, if its DNA is damaged, its chances of fulfilling its sole purpose are lowered.

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“Those with higher levels of sperm DNA damage (50% or higher) are more likely to have success using intracytoplasmic sperm injections (ICSI), as one sperm is injected directly into the woman’s egg. While IVF relies on the fittest egg of the bunch fertilising the egg, ICSI puts a damaged sperm directly into the egg, allowing the egg to fix the damaged sperm. Sperm heaven is sperm in an egg!”, continues Sheena.

The study is the first of its kind to look into the relationship between sperm DNA damage and the chances of having a baby using IVF or other treatments like intrauterine insemination (IUI).

According to Sheena, while sperm DNA damage is natural at a low level in all men, lifestyle factors can affect the damage.

“There are lots of factors that can affect sperm DNA. Smoking is very bad for sperm. Men who smoke have more effect on their fertility than women who smoke. Once sperm is damaged, the damage remains,” says Sheena.


Queen’s University Belfast has set up a company that enables men to have their sperm DNA damage measured. You will need a referral letter from your GP or fertility doctor. For more information go to