Sperm DNA fragmentation and male fertility: what it means for IVF and when to test

12 May 2026

Emma Whitney

Why standard sperm testing doesn’t always tell the whole story

Most couples start their fertility investigations in the same place:

A semen analysis looks at sperm count, movement, and shape. Hormone tests assess ovulation. An ultrasound checks the uterus and ovaries.

And for many people, those results lead to a clear path forward.

But for others, especially those who’ve already been through IVF or experienced unexplained loss, the numbers look fine on paper, and still something isn’t working. The embryos form, then don’t implant. Or they implant, and then you lose the pregnancy. Or cycle after cycle produces a result that no one can fully explain.

This is a particularly cruel kind of limbo. You’re doing everything right. The tests say everything looks normal. And yet.

Standard semen analysis measures how sperm look and move, but it doesn’t assess the quality of the genetic material inside. A sperm can appear perfectly normal under a microscope while carrying DNA that is fragmented, damaged, or unstable. And because sperm DNA contributes directly to the embryo, that fragmentation can affect everything that comes after: fertilisation, early development, implantation, and in some cases, the risk of miscarriage.

It doesn’t always cause problems. But in some patients, particularly those with unexplained failure, it’s a missing piece of the puzzle.

So what is sperm DNA fragmentation?

Every sperm cell carries half the genetic blueprint needed to build a baby: 23 chromosomes, tightly packed and protected inside the sperm head.

When fertilisation happens, those chromosomes join with the egg’s 23 chromosomes to create a complete set of 46, the genetic instructions that guide everything from early cell division to implantation, development, and the baby’s long-term health.

In healthy sperm, this genetic material is carefully organised and intact. But sometimes, strands of DNA can become damaged, developing breaks in the chromosome material that are invisible to a standard semen analysis. This is what we mean by DNA fragmentation.

It can happen even when sperm count and motility appear completely normal.

What causes sperm DNA fragmentation?

DNA fragmentation is most often associated with oxidative stress, essentially, damage caused by an imbalance between harmful free radicals and the body’s ability to neutralise them. Factors that can contribute include:

• Varicocele (enlarged veins in the scrotum)
• Smoking, alcohol, or vaping
• Obesity
• Prolonged exposure to heat
• Certain medications, including finasteride (used for male pattern baldness)
• Chronic illness or inflammation
• Environmental toxins
• Advanced paternal age
• Very long periods of abstinence

Sometimes there’s no single identifiable cause, which is precisely why testing can help clarify the picture rather than leaving you in uncertainty.

When is DNA fragmentation testing worth considering?

This isn’t a test we recommend routinely for everyone. But there are specific situations where it can provide genuinely useful information:

• After repeated failed IVF or ICSI cycles, particularly if embryo development or implantation hasn’t matched expectations, and no other explanation has emerged.
• After recurrent miscarriage, sperm DNA integrity can sometimes be a contributing factor, especially in recurrent early pregnancy loss.
• With unexplained infertility, when standard investigations haven’t given you an answer, a deeper look at sperm genetics may be the next logical step.
• Where there’s a known male fertility risk factor, such as varicocele, significant lifestyle factors, or a history of conditions that can affect sperm quality.

If you’re not in any of those categories and you’re at the beginning of your fertility journey, it’s likely not your first port of call. But if you’ve been here for a while and something isn’t adding up, it may well be worth the conversation.

How is sperm DNA tested?

A DNA fragmentation test is straightforward. It involves providing a sperm sample through ejaculation, which is then sent to a specialist andrology laboratory. The results are expressed as a fragmentation percentage, the proportion of sperm in the sample carrying damaged DNA.

There are several validated testing methods used internationally. One that some of our patients encounter is Examen’s Exact® Total Sperm DNA Fragmentation test, which directly measures both single and double-strand DNA breaks using a highly sensitive COMET-based assay. They also offer Extend®, which looks specifically at double-strand breaks, the type more commonly associated with miscarriage and repeated ART failure.

It doesn’t involve any surgical procedure, and it can often be arranged alongside other male fertility investigations.

Can high sperm DNA fragmentation be improved?

In many cases, yes, and that matters, because for some patients, this isn’t the end of the story but the beginning of a new approach.

Depending on the underlying cause, options may include:

• Stopping smoking, drinking, or vaping
• Weight optimisation
• Antioxidant therapy
• Treating any underlying infection or inflammation
• Varicocele repair, in selected cases
• Shortening abstinence periods before a cycle
• Advanced sperm selection techniques within ICSI
• Using testicular sperm in specific recurrent failure cases

One important thing to know: sperm production takes around three months to complete a full cycle. So improvements from lifestyle or treatment changes typically take about that long to show up in testing, which means starting early matters.

A note on the evidence

It’s important to be honest with you here. The evidence around sperm DNA fragmentation is not yet definitive, and it’s an evolving area of research. It is not currently included in the draft NICE guidelines for fertility treatment, and not every consultant will recommend it as standard.

That doesn’t mean it isn’t worth discussing. It means, as with so much in fertility medicine, that it needs to be considered in the context of your individual history, not applied as a blanket rule.

At The Evewell, we won’t push you towards testing that isn’t relevant to your situation. But if your story has unanswered questions that standard testing hasn’t addressed, we’ll tell you clearly when we think this might help.

The emotional side of male infertility

It would feel wrong to write this article without acknowledging something.

Many people who discover high DNA fragmentation do so after loss. After failed cycles. After months or years of trying. And with that comes a complicated mix of things: some relief at finally having an answer, and some grief, for the time, the embryos, the cycles that might have gone differently.

If that’s where you are, we want to make it clear: fertility medicine is always evolving, and sperm DNA integrity is an area where our understanding has grown significantly in recent years. Earlier tests may not have been available, or clinically indicated, or understood in the same way. None of that is a failure on your part, or anyone else’s.

What matters now is that you have information and a team that can help you decide what to do with it.

We’re here to help you make sense of this

Embryology, at its heart, is about understanding every factor that may affect your chance of a healthy pregnancy. A standard semen analysis is a good starting point, but it’s not always the final word.

If you’ve been through repeated IVF attempts, unexplained infertility, male infertility or pregnancy loss, sperm DNA fragmentation testing may be something worth discussing with your consultant and embryology team.

To speak with a member of our team, call us on 020 3974 0950 or visit our Support section for further guidance.