For many couples, the first fertility tests feel quite straightforward;
- A semen analysis looks at sperm count, movement and shape
- Hormone tests assess ovulation
- An ultrasound checks the uterus and ovaries
But for some patients, especially those who’ve already been through one or more unsuccessful IVF cycles, questions start to emerge that standard testing doesn’t always answer:
- Why do we keep making embryos but not getting pregnant?
- Why have we had repeated implantation failure?
- Could sperm quality be affecting embryo development?
- What is DNA fragmentation, and should we test for it?
This is often where sperm DNA fragmentation testing comes in.
It can provide an extra layer of information that isn’t visible through routine sperm testing, and for some patients, it can be a missing piece of the puzzle.
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What is sperm DNA fragmentation?
Sperm DNA fragmentation refers to damage or breaks within the genetic material carried inside the sperm.
To understand why this matters, it helps to know what sperm is actually delivering.
Every sperm cell contains tightly packed DNA, organised into chromosomes, which carry genetic instructions needed for embryo development.
Humans have 46 chromosomes in total, 23 from the egg and 23 from the sperm.
So when fertilisation happens, the embryo receives half its genetic blueprint from each parent.
This DNA includes thousands of genes that guide everything from early cell division to implantation, pregnancy development, and the baby’s long-term health.
In healthy sperm, this genetic material is carefully protected and compacted. But sometimes, strands of DNA in sperm can become damaged or fragmented, leading to breaks in the chromosome material. This can happen even when sperm look normal under the microscope.
A standard semen analysis measures things like:
- How many sperm are present
- How well they move
- Their shape and appearance
But it doesn’t assess whether the DNA inside the sperm is intact.
So a sperm sample can appear “normal” in terms of count and motility, while the genetic material inside some sperm cells may be less stable.
Because sperm DNA contributes directly to embryo genetics, fragmentation can affect:
- Fertilisation potential
- Embryo development in the lab
- Implantation
- Miscarriage risk in some cases
It’s one of the reasons why, for some couples, additional sperm testing becomes relevant after unexplained IVF failure or repeated pregnancy loss.
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What causes sperm DNA fragmentation?
DNA fragmentation is often associated with oxidative stress in sperm cells. Common contributing factors include:
- Varicocele (enlarged veins in the scrotum)
- Smoking or vaping
- Obesity
- High heat exposure
- Certain drugs (such as finasteride, used to treat male pattern baldness)
- Chronic illness or inflammation
- Environmental toxins
- Advanced paternal age
- Long periods of abstinence
Sometimes, no single clear cause is found, which is why testing can help clarify the situation.
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Why don’t we detect DNA fragmentation sooner?
Many people assume that if the semen analysis is “normal,” sperm quality isn’t part of the issue.
But a standard semen analysis doesn’t assess DNA integrity, so DNA fragmentation can go unnoticed until couples experience:
- Unexplained infertility
- Recurrent miscarriage
- Poor embryo development
- Failed IVF or ICSI cycles despite good eggs
It’s very common for patients to only discover this after multiple attempts, which can feel frustrating, especially when you’ve already been through so much.
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What is a sperm DNA fragmentation test?
A sperm DNA fragmentation test measures the proportion of sperm in a sample that carries damaged or fragmented DNA.
Unlike standard semen analysis, which focuses on sperm count and movement, this is a deeper assessment of sperm genetic integrity.
There are several testing methods used internationally, including:
- COMET assay
- TUNEL assay
- SCSA testing
- SCD testing
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Examen’s Exact® Total Sperm DNA Fragmentation test
One advanced test that some patients may encounter is Examen’s Exact® Total Sperm DNA Fragmentation test.
Examen describes this as a direct measurement of sperm DNA damage, assessing both single and double-strand breaks, using a highly sensitive COMET-based assay.
They also offer Extend®, which focuses specifically on double-strand breaks, which may be more strongly associated with miscarriage and repeated ART failure.
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What does the test involve?
A DNA fragmentation test typically involves:
- Providing a sperm sample through ejaculation
- The sample being sent to a specialised andrology laboratory, such as Examen
- DNA integrity assessed using a validated assay
- Results reported as a fragmentation percentage or score
It doesn’t involve surgery, and it can often be arranged alongside other male fertility testing.
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When should you consider DNA fragmentation testing?
In general, DNA fragmentation testing may be worth discussing if:
- You’ve had repeated failed IVF or ICSI cycles, especially if embryo development or implantation hasn’t matched expectations.
- You’ve experienced recurrent miscarriage, as sperm DNA integrity can sometimes be a contributing factor.
- You have unexplained infertility, and when standard investigations haven’t provided an answer.
- There’s a known male fertility risk factor, such as varicocele, smoking, or significant oxidative stress.
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Can high DNA fragmentation be treated?
In many cases, there are steps that can improve sperm DNA integrity. Treatment options depend on the underlying cause, but may include:
- Lifestyle changes (stopping drinking, smoking and vaping, weight optimisation)
- Antioxidant therapy
- Treating infection or inflammation
- Varicocele repair in selected cases
- Shortening abstinence periods
- Using advanced sperm selection techniques such as ICSI
- Considering testicular sperm in specific recurrent failure cases
Often, improvements take about three months because sperm production cycles take about that long.
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Why this matters emotionally as well as medically
One of the hardest things about DNA fragmentation is that people often discover it after disappointment.
After failed cycles, it’s natural to ask:
- Was something missed?
- Could we have tested sooner?
- Is this why IVF hasn’t worked yet?
It’s important to remember that fertility care is constantly evolving, and sperm DNA integrity is an area where awareness and evidence have grown significantly in recent years.
For some couples, testing provides answers and new options. For others, it provides reassurance.
Either way, it helps us make more personalised decisions moving forward.
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A final note from the lab
At The Evewell, embryology is not just about creating embryos; it’s about understanding every factor that may affect the chance of a healthy pregnancy.
If you’ve been through repeated IVF attempts, unexplained infertility, or loss, sperm DNA fragmentation testing may be something worth discussing with your consultant and embryology team.
Please note that the evidence around DNA is not entirely clear, which is why it has not been included in the draft NICE guidelines for now.
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