Sperm Morphology: What Sperm Shape Really Means for Fertility
Sperm morphology looks at the shape and structure of sperm — and it’s one of the most misunderstood parts of a semen analysis. If you’ve been told your morphology is “low,” this guide will help you understand what that actually means, what matters next, and how to move forward with clarity.
Author
Tassia O’Callaghan
Reviewed by
Kayleigh Hartigan
18 min read
Published 16 January 2026
Spotlight:
- Sperm morphology looks at sperm shape — not how many sperm you have or how fast they swim. Even low percentages can still be compatible with pregnancy.
- Low sperm morphology is very common and often misunderstood. It’s one of the most frequent findings on a semen analysis and rarely tells the full fertility story on its own.
- Lifestyle, health, and recent illness can influence morphology. Because sperm are constantly regenerating, results can change over time.
- Morphology is assessed as part of a semen analysis using strict lab criteria. Results reflect how many sperm meet an “ideal” definition — not how many can fertilise an egg.
- Conception is possible even with very low morphology. Outcomes depend on the wider picture, including count, motility, egg health, and timing.
- When morphology is low, treatments like IUI or IVF (especially ICSI) may be able to work around it. The right next step depends on context, not a single number.
What is sperm morphology?
Sperm morphology describes how sperm look under a microscope. A sperm with “normal” morphology has an oval head (with intact DNA packaging), a well-defined midpiece, and a single, straight tail. [1]
Abnormal sperm morphology means a higher proportion of sperm have shape differences — for example, large or small heads, double heads, bent necks, or coiled tails. You might see this referred to as teratozoospermia, abnormal shaped sperm, or deformed sperm.
Importantly, morphology doesn’t tell us whether all sperm are abnormal; it tells us what percentage look typical by strict criteria.
Can lifestyle affect sperm morphology?
Yes — lifestyle and overall health can influence sperm shape, sometimes more than people expect. Sperm are produced continuously, and the process is sensitive to physical stress, illness, and environmental factors, which means changes can show up in morphology results over time.
- Smoking and vaping: Tobacco exposure is consistently linked with higher rates of abnormal sperm morphology. The toxins involved can interfere with sperm development and DNA packaging. [2]
- Alcohol intake: Regular or high alcohol consumption can disrupt hormone balance and sperm production, which may affect morphology as well as count and motility. [2]
- Heat exposure: Frequent use of hot tubs, saunas, heated car seats, or placing laptops directly on the lap can raise testicular temperature. Sperm production requires a slightly cooler environment, and excess heat can affect sperm shape. [3]
- Body weight and metabolic health: Obesity and insulin resistance are associated with changes in hormone signalling and increased oxidative stress, both of which can contribute to abnormal sperm morphology. [2]
- Illness, fever, or inflammation: Even short-term illness — such as a high fever or viral infection — can temporarily impact sperm shape. This is one reason a single test doesn’t always tell the full story. [4]
- Environmental and occupational exposures: Certain chemicals, pesticides, heavy metals, and solvents have been linked to sperm abnormalities, particularly with long-term or repeated exposure. [5]
Male Fertility Tests & Sperm Tests
Male factor fertility issues play a role in around 50% of couples struggling to conceive — but are often overlooked in the early stages of testing.
Who is a sperm morphology test for?
A sperm morphology test can be a helpful next step to understand whether sperm shape could be playing a role, and what that means in the context of your wider fertility picture.
A morphology assessment may be particularly relevant if:
- You’ve been trying to conceive for 12 months (or 6 months if your partner is over 35): At this point, fertility guidelines suggest looking more closely at both sides of the equation with a fertility MOT (basic fertility tests for men and women). Assessing sperm morphology can help identify subtle male-factor issues that aren’t always obvious early on. [6]
- There’s unexplained infertility despite normal count and motility: When sperm numbers and movement look fine, morphology can offer additional insight. Shape affects how sperm interact with the egg, so this test can sometimes explain why conception hasn’t happened yet.
- You’re planning IUI or IVF and want a fuller picture: Morphology results can help clinics decide which treatment approach may be most appropriate, including whether techniques like ICSI could improve fertilisation outcomes.
- There’s a history of miscarriage or poor embryo development: While morphology alone might not be the sole cause, understanding sperm shape can form part of a broader investigation into embryo quality and early development.
- You’ve had previous semen analyses with borderline or low results: Because morphology can fluctuate, repeat or more detailed testing can confirm whether a pattern is emerging and whether further investigation or support would be useful.
How is sperm morphology tested?
Sperm morphology is assessed as part of a standard semen analysis, using established laboratory methods rather than subjective judgement. The process is highly technical and carried out by trained embryologists, which is why results are best interpreted in context rather than taken at face value.
In the lab, a sperm sample is stained and examined under high magnification. Hundreds of sperm are assessed against strict criteria — most commonly the Kruger “strict” method — and the result is reported as the percentage of sperm that meet the definition of a typical shape. [7]
Here’s how the process usually works:
- Sample collection: The sample is collected after a short period of abstinence (usually 2 to 7 days), usually at a clinic to ensure optimal handling. Some clinics also offer home collection kits, as long as the sample can reach the lab within a specific time window.
- Preparation and staining: In the laboratory, the sample is prepared and stained so the fine details of each sperm — particularly the head, midpiece, and tail — can be clearly seen under a microscope.
- Microscopic assessment by an embryologist: A trained embryologist examines hundreds of sperm individually, looking for specific features such as head size and shape, neck alignment, and tail structure. This step requires expertise, as the criteria are deliberately strict (although in the near future, more clinics may use trained AI to help with this step). [8]
- Percentage score of normally-shaped sperm: The final result is given as a percentage. This reflects how many sperm meet the strict definition of “normal,” not how many are capable of fertilising an egg.
Because sperm production is ongoing and influenced by health, illness, and lifestyle, morphology can vary between samples. For that reason, clinics sometimes recommend repeat testing before drawing conclusions or making treatment decisions — or after lifestyle or health changes. [4]
Can I ask my GP for a sperm morphology test?
Yes. In the UK, a GP can request a basic semen analysis through the NHS, and this usually includes sperm morphology. For some people, this is a reasonable first step — particularly if you’re early in the process or want an initial screen. That said, NHS testing isn’t always designed for detailed fertility decision-making. Waiting times can be lengthy, results are often reported in a simplified way, and accessing repeat testing or follow-up discussions can be challenging.
Because of this, many people choose to have sperm morphology assessed at a private fertility clinic. Private testing is typically faster, results are explained in more depth, and findings can be reviewed alongside other fertility factors rather than in isolation. If you’re feeling time pressure, navigating ongoing uncertainty, or already considering treatment options, this added clarity can make a meaningful difference.
Can I check my sperm morphology at home?
Unfortunately not. At-home semen testing kits are available, and some can provide a basic assessment of sperm health. The instant at-home sperm testing kits only test for sperm count and motility, not morphology. This is because morphology is one of the hardest parameters to assess accurately outside a specialist lab. Any at-home semen testing kits that offer morphology testing would need to be sent away to a lab, which can take some time, and outside influences (like a particularly hot day) might mean that the semen sample could be compromised by the time it gets to the lab, if it has to be posted.
Can I get my sperm morphology checked at a private fertility clinic?
Yes. Private fertility clinics routinely assess sperm morphology as part of a comprehensive semen analysis. Testing is usually straightforward to arrange, results are returned quickly, and you’ll typically have the opportunity to discuss what they mean in the context of your wider fertility picture. This can be particularly valuable if you’re planning IUI or IVF, have had previous unclear results, or want reassurance that nothing important is being missed.
If you do decide to explore private testing or next steps, our team at Seen Fertility can help you find a clinic that truly fits your needs — matching you to options based on your results, priorities, location, and the kind of care you’re looking for, so you can move forward with confidence rather than guesswork. Not sure where to start? Have a chat with one of our fertility clinic experts.
Find the right clinic for you
Choosing a clinic is one of the biggest decisions you’ll make. We’ll help find the best options for you, whatever your journey.
How much does a sperm morphology test cost?
In the UK, sperm morphology is usually assessed as part of a semen analysis, rather than as a standalone test. From figures in our 2026 Cost of IVF report, private semen analysis costs typically range from £105 to £195, with an average cost of around £165. This price usually includes sperm count, motility, and morphology assessed using standard laboratory criteria. [9]
Costs can increase if repeat testing is recommended or if more advanced analysis is needed, particularly when results are borderline or don’t align with the wider fertility picture. Prices also vary by clinic and location, reflecting differences in lab facilities, reporting depth, and consultation time.
Some clinics offer fertility MOTs that bundle semen analysis with hormone blood tests, ultrasounds, or clinical consultations. For many people, these packages provide better value—not because more tests are always needed, but because results are reviewed together, helping to reduce uncertainty and avoid fragmented decision-making.
Understanding sperm morphology test results
Sperm morphology results can feel confronting at first, especially when the numbers are small. What matters most is understanding what those percentages actually represent, how they’re defined, and how much weight they should carry alongside the rest of your fertility information.
According to the Kruger “strict” method, as suggested by the World Health Organization, results are typically split two ways: [7]
- Low sperm morphology: Less than 4%
- Normal sperm morphology: 4% or more
What is a ‘normal’ sperm morphology level?
Using strict criteria, sperm morphology is considered within the normal range when 4% or more of sperm have a typical shape. This doesn’t mean that 96% of sperm are “bad,” or unable to do their job. It simply reflects how demanding the assessment criteria are. Under strict analysis, only sperm that meet very precise standards for head, midpiece, and tail structure are counted as normal.
In practical terms, if 100 sperm are assessed and 4 meet those criteria, that result falls within the expected range. The remaining sperm may have minor shape differences that are still compatible with fertilisation. This threshold is based on international standards, including guidance aligned with the World Health Organization, and is used globally to help laboratories interpret results consistently. [7]
What do ‘low’ sperm morphology levels mean?
Low sperm morphology generally refers to results below 4% normal forms. You may see results like:
- 3% — borderline
- 1–2% — low
- 0% — no sperm met strict criteria in that sample (also known as teratozoospermia)
While those numbers can sound alarming, they are far more common than many people realise.
Low morphology does not mean sperm cannot fertilise an egg. Many people conceive naturally with low morphology, particularly when sperm count and motility are strong. Morphology tells us about the proportion of sperm with an “ideal” shape — it doesn’t measure determination, DNA competence in isolation, or the likelihood of pregnancy on its own.
This is especially relevant if you have high sperm count but low morphology, a combination that can raise questions about fertilisation efficiency without automatically pointing to a problem. In these situations, understanding how the results interact — and what they mean for natural conception, IUI, or IVF — is far more valuable than focusing on one number alone.
Can you conceive with 2% sperm morphology or less?
Yes. Conception is absolutely possible with 2% morphology, even with 0% morphology. What matters most is the whole fertility picture, including sperm numbers, movement, egg health, timing, and how long you’ve been trying. Morphology is one piece of information, not a verdict.
What do ‘high’ sperm morphology levels mean?
Higher morphology results indicate that a larger proportion of sperm meet strict shape criteria. This can feel reassuring and may suggest fewer barriers at the fertilisation stage, but it’s not a guarantee of pregnancy. Fertility doesn’t work on a single metric, and even strong-looking results need to be interpreted alongside other factors.
It’s also worth noting that many clinics don’t have an upper threshold for what’s classed as “high” morphology — it’s usually seen as either “normal” or “low.”
Can sperm morphology be improved?
Sometimes, yes. Whether sperm morphology can improve depends on what’s driving the abnormality in the first place. For some people, morphology is influenced by health, lifestyle, or environmental factors that can be modified over time. For others, it reflects underlying biological patterns that are less changeable, but still very manageable within fertility treatment.
How can I improve my sperm morphology?
When improvement is possible, the focus is usually on supporting overall sperm health, rather than targeting morphology in isolation. These steps are often recommended alongside clinical guidance:
- Stop smoking and reduce (or stop entirely) alcohol intake: This is one of the most impactful changes for sperm health and can improve multiple semen parameters at once, including morphology. [2]
- Optimise sleep, movement, and nutrition: Regular sleep, gentle but consistent exercise, and a balanced diet help regulate hormones and reduce inflammation, creating a healthier environment for sperm development. [2]
- Address vitamin and nutrient deficiencies with clinician guidance: Deficiencies in nutrients such as zinc, selenium, and folate may affect sperm structure. Supplementation should always be guided by a healthcare professional rather than taken blindly. [10]
- Reduce heat and toxin exposure: Simple changes — like avoiding prolonged heat exposure (like hot tubs and saunas) and using protective equipment in certain work environments — can support healthier sperm production over time. [2]
Is low sperm morphology reversible?
In some cases, yes — particularly when low morphology is linked to modifiable lifestyle or environmental factors. Because sperm take an average of 74 days (but possibly as low as 42 days) to develop from start to finish, any changes you make now won’t show up immediately. Clinics often recommend allowing at least one full sperm cycle before retesting, to assess whether improvements have occurred. [11]
Are there medications to help morphology?
There is no single medication proven to directly “fix” sperm morphology. Instead, treatment focuses on addressing underlying causes where they exist. This may include treating infection, managing hormonal imbalances, or surgically correcting a varicocele. When morphology remains low despite these steps, assisted fertility treatments can help work around the issue rather than trying to force a biological change that may not be achievable.
Next steps after a sperm morphology test
Getting sperm morphology results can trigger a lot of questions, but this stage is about turning information into direction. The aim isn’t to react to a single percentage — it’s to understand what, if anything, needs to happen next and which options genuinely make sense for you.
Here’s how those next steps are usually approached:
- Repeat the test if results are borderline or unexpected: Sperm morphology can fluctuate from sample to sample due to illness, stress, or timing. A repeat test helps confirm whether the result reflects an ongoing pattern or a temporary dip.
- Review results in context: Morphology should never be looked at in isolation. Sperm count, motility, timing, and egg-related factors all play a role in fertilisation, and strong results elsewhere can significantly offset low morphology.
- Consider specialist input if results are persistently low: If repeat tests show consistently low morphology, a fertility specialist or urologist can help explore possible causes and advise whether further investigation is worthwhile.
- Discuss whether IUI, IVF, or ICSI may improve chances: Assisted fertility treatments aren’t automatic next steps, but they can be powerful tools when morphology is affecting fertilisation. The right approach depends on how low morphology is, how long you’ve been trying, and your wider fertility picture.
- Focus on what’s actionable now, not just the number: This might mean lifestyle changes, further testing, or simply reassurance that no immediate intervention is needed. Clarity often comes from knowing what you don’t need to do as much as what you do.
Is IUI good for low morphology?
IUI can be effective for mildly low sperm morphology, particularly when sperm count and motility are strong. Because IUI relies on sperm fertilising the egg naturally, success rates tend to decrease as morphology becomes more severely reduced. In these cases, clinics may recommend alternative approaches earlier.
Can you do IVF with 0% morphology?
Yes. IVF — especially with ICSI (intracytoplasmic sperm injection) — is commonly used when morphology is very low or reported as 0%. With ICSI, an embryologist selects a single sperm and injects it directly into the egg, bypassing many of the barriers that abnormal shape can create.
Does sperm washing help morphology?
Sperm washing doesn’t change the shape of sperm, but it does help concentrate the healthiest, most motile sperm from a sample. This process can improve the quality of sperm used in IUI or IVF and reduce debris or non-viable sperm, supporting better treatment conditions even when morphology is low. [12]
Why sperm morphology matters — and why it’s rarely the whole story
Sperm morphology testing matters because it offers insight into how sperm may function at the point of fertilisation, but it was never designed to stand alone. Low morphology results are common, frequently misunderstood, and often carry more emotional weight than they deserve. On their own, they rarely explain everything that’s happening, and they certainly don’t define what is or isn’t possible.
When morphology is viewed in context — alongside sperm count, motility, egg health, timing, and how long you’ve been trying — it becomes something far more useful than a number. It becomes information that helps guide decisions, shape conversations with specialists, and clarify which options are genuinely worth considering next. For some people, that means reassurance and time. For others, it means targeted support or treatment that works around the issue rather than fighting it.
If you’re navigating male factor fertility concerns, it’s important to know this isn’t unusual, and it isn’t something you have to interpret alone. With thoughtful care and the right fertility clinic fit, sperm morphology stops being a source of confusion and starts becoming a tool — one that helps you move forward with confidence and a plan that reflects your full fertility picture.
Sperm morphology FAQs
How common is poor sperm morphology?
Very common. It’s one of the most frequent “abnormal” findings on a semen analysis. This is partly because morphology uses very strict criteria, meaning many perfectly functional sperm are still classed as abnormal. Seeing a low percentage can feel alarming, but in practice it’s something fertility specialists encounter every day and often manage without it becoming a barrier to pregnancy. In fact, the WHO threshold used to be anything less than 14% to be considered low sperm morphology! [13]
Does sperm morphology get worse with age?
There can be a gradual decline in sperm quality, including morphology, as age increases, but age alone is rarely the full explanation. Lifestyle factors, general health, environmental exposures, and periods of illness often have a much stronger influence on sperm shape than the number of birthdays someone has had. This is why two people of the same age can have very different results, and why changes over time don’t always follow a straight line.
Can sperm morphology cause miscarriage?
On its own, low sperm morphology isn’t strongly linked to miscarriage. Most early pregnancy loss is related to chromosomal issues in the embryo, which are influenced by many factors on both sides. In some cases, severe male factor infertility combined with higher levels of sperm DNA damage may contribute, which is why further testing can be useful if there’s a history of recurrent miscarriage or unexplained loss. [14]
Can morphology cause birth defects?
There is no clear evidence that low sperm morphology by itself increases the risk of birth defects. While abnormal shape can affect how sperm reach or fertilise an egg, it doesn’t mean that sperm capable of fertilisation carry a higher risk of structural problems in a pregnancy. This distinction is important, as morphology results often sound more concerning than they actually are.
Does sperm morphology affect embryo quality?
Sperm morphology can influence fertilisation rates, particularly in natural conception or IUI, where sperm must complete every step on their own. But once fertilisation has occurred and an embryo is developing, morphology becomes far less predictive. At that stage, factors such as egg quality, embryo genetics, and chromosomal health play a much larger role in how an embryo develops and whether a pregnancy continues.
Sources
- Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science; 2002. Sperm. Available from: https://www.ncbi.nlm.nih.gov/books/NBK26914/
- NHS University Hospitals Birmingham, NHS Foundation Trust. Improving sperm quality. Issue date: April 2023.
- NHS Manchester University, NHS Foundation Trust. Healthy Living — Preparing for Pregnancy. Updated December 2023.
- The Shrewsbury and Telford Hospital, NHS Trust. Sperm Function Test Results & Lifestyle Advice To Men Who Are Trying To Conceive.
- NHS 111 Wales. Low sperm count (oligozoospermia). Last updated 09/10/2025.
- NHS. Infertility. Last reviewed 09 August 2023.
- World Health Organization. WHO laboratory manual for the Examination and processing of human semen, Fifth edition. 2010.
- Jaruenpunyasak J, Maneelert P, Nawae M, Choksuchat C. Artificial intelligence model for the assessment of unstained live sperm morphology. Reprod Fertil. 2025 May 2;6(2):e250014. doi: 10.1530/RAF-25-0014. PMID: 40261982; PMCID: PMC12060770.
- Seen Fertility. How Much Does IVF Cost in the UK? (Updated for 2026). Updated 18 November 2025.
- Wong, W.Y., Thomas, C.M., Merkus, J.M., Zielhuis, G.A. and Steegers-Theunissen, R.P., 2000. Male factor subfertility: possible causes and the impact of nutritional factors. Fertility and sterility, 73(3), pp.435-442.
- University of California San Francisco. Archive: New Findings on Sperm Life Cycle Could Impact Fertility Treatments. March 16 2006.
- Human Fertilisation & Embryology Authority. Intrauterine insemination (IUI). Published 11 March 2016.
- IVFMD Texas. New World Health Semen Analysis Parameters.
- Tommy’s. The effect of sperm damage in miscarriage.