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Teratozoospermia: Causes, Symptoms, and Fertility Treatment Options

Teratozoospermia is a condition where a high percentage of sperm have abnormal shapes. Because sperm morphology plays a role in fertilisation, this diagnosis can raise understandable concerns about fertility — but it doesn’t rule out the possibility of pregnancy.

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Author

Tassia O’Callaghan

Reviewed by

Kayleigh Hartigan

16 min read

Updated 2nd October 2025

Condition spotlight:

  • Teratozoospermia means a high proportion of sperm are abnormally shaped, affecting the head, midpiece, or tail.

  • Normal reference range is ≥4% normal forms, according to the World Health Organization — anything below this may be diagnosed as teratozoospermia. [1,2,3]

  • There are no physical symptoms; most people only find out after a semen analysis during fertility testing.

  • Causes are varied, from lifestyle and environmental factors (smoking, alcohol, heat, toxins) to medical conditions, infections, or — in rare cases — genetics.

  • Impact on fertility is mixed: some men with very low morphology still conceive naturally, while others may need fertility treatment.

  • Treatment options range from lifestyle changes and supplements to assisted reproductive techniques like IUI, IVF, or ICSI, depending on the severity and other sperm parameters.

What is teratozoospermia?

Teratozoospermia (sometimes called teratospermia) is a male fertility condition where a high proportion of sperm have an irregular shape. [4,5]

This could involve: [6]

  • Abnormal head (too large, too small, irregular, or multiple heads)

  • Abnormal midpiece (too thick, too thin, or misshapen)

  • Abnormal tail (short, coiled, or multiple tails)

Doctors measure this using sperm morphology — the percentage of sperm that look “normal” under a microscope. According to the World Health Organization (WHO), a semen sample is considered within the normal range if at least 4% of sperm have a typical shape. Anything below this is diagnosed as teratozoospermia. [7]

What causes teratozoospermia?

There isn’t always a single explanation, and more than one factor can be at play. Causes (and plausibility) include:

  • Infections (especially untreated STIs): Chlamydia and other genital tract infections can inflame the testes/epididymis and directly damage sperm, with reports of altered morphology and higher DNA fragmentation; prompt diagnosis and antibiotics may help. [8,9]

  • Varicocele (enlarged scrotal veins): Varicoceles can raise testicular temperature and impair semen quality, including morphology; repair may improve fertility/semen parameters in selected cases (evidence is mixed). [10]

  • Environmental exposures (heat, chemicals, radiation): Excess heat (saunas/hot baths, tight underwear, hot workplaces) and some pesticides/solvents/heavy metals are linked with poorer semen quality; NHS advises minimising such exposures when trying to conceive. [11,12]

  • Smoking (tobacco/vaping): Smoking is consistently associated with worse semen parameters (including morphology); NHS trusts advise avoiding tobacco and e-cigarettes when trying to conceive. [13,14]

  • Alcohol (especially heavy intake): NHS recommends staying within UK low-risk guidelines; heavy or chronic use relates to poorer semen quality and worse reproductive outcomes. [12,15]

  • Recreational/illicit drugs & anabolic steroids: NHS specifically warns that anabolic steroids and certain illegal drugs (e.g., cocaine) can impair sperm production and quality; stop and seek medical advice if relevant. [16,17]

  • Poor diet & excess weight: NHS and professional bodies highlight weight and dietary pattern as modifiable factors for male fertility; a balanced diet and healthy BMI are advised. [8]

  • Medical conditions such diabetes, endocrine disorders: Systemic illness and hypogonadism can reduce semen quality; managing the underlying condition is part of care pathways. [18,19,20]

  • Medications and cancer treatments: Cytotoxic chemotherapy and pelvic radiotherapy can cause lasting testicular damage and abnormal sperm; UK guidance stresses pre-treatment sperm freezing discussions. [21]

  • Workplace or environmental toxins: Where relevant, NHS advises reducing exposure to pesticides/solvents/heavy metals that have been associated with poorer semen quality. [22,23]

  • Genetic factors: Certain chromosomal or gene changes can disrupt spermatogenesis and increase abnormal sperm forms (such as Klinefelter syndrome and Y-chromosome microdeletions). Genetic factors aren’t the most common cause of male fertility issues, but they are a recognised contributor in some cases. [24,25,26]

Can abstinence cause teratozoospermia?

No — abstinence itself doesn’t cause teratozoospermia, but the length of time between ejaculations can affect how sperm look under the microscope. If you go longer than seven days without ejaculating, sperm quality — including morphology — may start to decline, which could make teratozoospermia appear more pronounced in a semen analysis. That’s why clinics usually ask for a sample after at least 2 days of abstinence, but no more than 7, to give the most accurate picture of sperm health. [27,28]

Can cycling cause teratozoospermia?

Cycling has often been questioned as a possible factor in sperm health, mainly because long hours in the saddle can increase scrotal temperature and put pressure on the testicles. While some studies suggest this may affect sperm quality, including morphology, the evidence isn’t strong enough to say cycling directly causes teratozoospermia. For most people, moderate cycling as part of an active lifestyle is unlikely to be harmful. If you’re cycling at high intensity or for prolonged periods, it may be worth making small adjustments — like padded shorts, frequent breaks, or varying exercise — to keep things comfortable and reduce heat build-up. [23,29]

Can stress cause teratozoospermia?

Stress can influence sperm health, but it’s important to distinguish between two different types. Psychological stress — the kind linked to work, relationships, or daily pressures — doesn’t directly “cause” teratozoospermia, though it may affect sex drive, routine, and overall wellbeing, which can indirectly impact fertility. [8]

Oxidative stress, on the other hand, happens inside the body when there’s an imbalance between free radicals (reactive oxygen species) and antioxidants. Research shows that high oxidative stress in semen is closely linked to abnormal sperm morphology, suggesting it may play a role in teratozoospermia. While the exact mechanisms are still being studied, supporting both emotional wellbeing and physical health can help create better conditions for sperm quality. [30]

What are the symptoms of teratozoospermia?

Teratozoospermia doesn’t cause any obvious physical symptoms. You won’t notice changes in how you feel, look, or function sexually. Most people only find out after a semen analysis, which is usually recommended if pregnancy hasn’t happened after a year of trying.

Testing is usually suggested if you notice things like:

  • Difficulty conceiving after 12+ months of regular, unprotected sex. Around 1 in 7 couples experience this in the UK, and sperm abnormalities such as morphology are one possible reason. [8]

  • Recurrent pregnancy loss. Research shows that in some cases, abnormal sperm shape can be linked with DNA damage, which may increase the risk of miscarriage. [31,32]

  • Unexpected outcomes during fertility treatment. For example, low fertilisation rates in IVF or IUI may prompt a closer look at sperm morphology.

Because teratozoospermia doesn’t show up in day-to-day life, testing is the only way to confirm whether it’s present.

Can teratozoospermia affect fertility?

Yes, teratozoospermia can affect fertility, but the picture isn’t straightforward. Because sperm morphology is just one part of overall sperm health, abnormal shape alone doesn’t always mean pregnancy isn’t possible. Some men with very low percentages of normally shaped sperm still conceive naturally, while others face more difficulty.

Research suggests that severe teratozoospermia may be linked with lower fertilisation rates, poorer embryo development, and, in some cases, a higher risk of miscarriage due to sperm DNA damage. At the same time, other studies show that when sperm count and motility are otherwise normal, isolated teratozoospermia may not significantly reduce chances of conception, either naturally or with treatments like IUI and IVF. [33,34,35,36]

Ultimately, morphology is best viewed alongside other factors — such as sperm motility, DNA quality, and female partner’s fertility — to understand its true impact.

What’s the typical pregnancy rate with teratozoospermia?

There isn’t one clear “typical” pregnancy rate with teratozoospermia, because outcomes vary widely depending on how severe the morphology issue is and whether other sperm parameters are normal. Research shows that even when sperm morphology is extremely low — including cases with 0% normal forms — natural conception is still possible, with some studies reporting pregnancy rates of around 20–30% over time. [35]

Other research has suggested similar figures, with occasional reports as high as 39% in certain groups. What this tells us is that abnormal sperm shape on its own doesn’t always prevent conception, though chances can be lower and it may take longer.

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.

Find out more

How do you test for teratozoospermia?

A semen analysis is the standard way to diagnose teratozoospermia, and while the test itself is simple, preparing properly makes a big difference to how accurate the results are. Before your appointment, you’ll usually be asked to abstain from ejaculation for 2–7 days — three to four days is often considered ideal. This means no sex or masturbation during that time. Any longer than seven days can reduce sperm quality, and less than 48 hours may not give the most reliable result. [28]

On the day, you’ll be given a sterile container (it’s important not to use any other pot, as everyday plastics and lubricants can damage sperm). The sample is usually produced in a private room at the clinic by masturbation. If producing a sample on site feels difficult, some clinics allow you to collect at home, provided the sample can be delivered to the lab within an hour and kept at body temperature — for example, by carrying it in an inside pocket. Condoms and regular lubricants can’t be used, as they can kill sperm, but clinics can provide non-toxic options if needed. [37]

Once your sample is handed over, it’s analysed in the lab according to World Health Organization (WHO) standards. Scientists will check the semen volume, sperm concentration (number of sperm), motility (movement), and morphology (shape). Because sperm quality can fluctuate, your doctor may recommend repeating the test at least once more before making a diagnosis. [38]

Can you get tested for teratozoospermia with the NHS?

Yes. If you and your partner have been trying to conceive for a year (or six months if your partner is over 35) without success, your GP can refer you for fertility tests on the NHS. This usually starts with a semen analysis, which looks at sperm count, movement (motility), and shape (morphology) — the measure used to diagnose teratozoospermia. [4,12,28]

If sperm abnormalities are found, you may then be referred to a specialist fertility clinic for further tests, which could include blood work, genetic screening, or ultrasound scans.

What are the different grades of teratozoospermia?

There isn’t one universal grading system for teratozoospermia, but doctors often describe it based on the percentage of sperm that appear normally shaped in a semen analysis. The World Health Organization (WHO) uses 4% or more normal forms as the reference point. Anything below that may be diagnosed as teratozoospermia, with some clinics and studies breaking it down further:

  • Normal morphology: ≥4% of sperm appear normally shaped (no teratozoospermia).

  • Mild teratozoospermia: Just under the 4% threshold (for example, 2–3% normal forms).

  • Moderate teratozoospermia: Around 1–2% normal forms.

  • Severe teratozoospermia: 0–1% normal forms.
 

These categories aren’t officially standardised worldwide, but they help describe the degree of abnormality. The lower the percentage of normally shaped sperm, the more likely it is to impact fertility — though outcomes also depend on other factors like sperm count, motility, and the fertility of the female partner. [3,39,40]

Can you treat teratozoospermia?

There isn’t one single treatment for teratozoospermia, because the approach depends on what’s driving the abnormal sperm morphology in the first place. For some men, making lifestyle changes or addressing a medical condition can improve sperm health over time. For others, assisted reproductive techniques may still be the most effective way forward.

  • Lifestyle changes: Quitting smoking, limiting alcohol, maintaining a healthy weight, eating a balanced diet, and keeping active are all linked to better sperm quality. [12,29,41]

  • Treating underlying conditions: Conditions such as diabetes, untreated infections (including STIs), or varicocele (enlarged veins in the scrotum) can negatively affect sperm shape. Managing or treating these issues may lead to improvements in sperm morphology. [42]

  • Supplements and antioxidants: Research suggests that Coenzyme Q10, vitamins C and E, zinc, selenium, and folic acid may support sperm health by reducing oxidative stress, though evidence is mixed and results are not guarantee. Supplements may be suggested alongside lifestyle changes, rather than as a stand-alone fix. [43,44,45,46]

  • Medical treatments: If an underlying cause is identified, specific medical treatments may be offered. For example, antibiotics can be prescribed for infections, surgery may be recommended for varicocele, and hormone therapy could be considered in cases of hormonal imbalance.

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How does teratozoospermia affect fertility treatment?

Teratozoospermia doesn’t rule out fertility treatment, but it can influence which options are most effective. Different treatments approach sperm shape in different ways, so recommendations often depend on how severe the morphology issue is alongside other sperm parameters.

IUI (Intrauterine insemination)

IUI can still be an option when sperm morphology is low, especially if sperm count and motility are otherwise normal. In the lab, sperm are carefully prepared so that the healthiest, best-moving ones are concentrated before insemination.

Research suggests that isolated teratozoospermia (where only sperm shape is abnormal, but count and motility are normal) may reduce the overall chances of success compared with men whose sperm are within normal ranges. A large study found that couples with isolated teratozoospermia had a cumulative live birth rate of around 33% after four IUI cycles, compared with about 53% in couples with normal semen parameters. This means that while pregnancy is possible, outcomes per cycle may be lower and some clinics may recommend moving to IVF or ICSI sooner, particularly if conception hasn’t happened after several rounds of IUI. [33]

For couples considering IUI, it’s worth discussing how sperm morphology interacts with other factors, like female age and overall fertility health, to decide whether IUI is a good starting point or whether more advanced treatments might offer higher chances of success.

IVF

With conventional IVF, eggs and sperm are placed together in the lab so fertilisation can happen naturally. For men with severe teratozoospermia, some clinics may be cautious about relying on IVF alone, as abnormal morphology can sometimes be linked to lower fertilisation rates. However, the evidence isn’t entirely straightforward.

One study looking at more than 500 IVF cycles found that isolated teratozoospermia (abnormal shape only, with otherwise normal count and motility) did not reduce fertilisation, pregnancy, or live birth rates compared with men who had normal semen parameters. In fact, outcomes were no better when these couples used ICSI instead of IVF, suggesting that ICSI may not always be necessary if sperm count and motility are otherwise healthy. [47]

This means that IVF alone can still be effective in many cases of teratozoospermia, particularly when it is the only sperm parameter outside of the normal range. Clinics will often weigh sperm morphology alongside other factors — such as motility, count, DNA quality, and the female partner’s fertility profile — when deciding whether conventional IVF or IVF with ICSI is the best next step.

Is teratozoospermia the only reason for IVF failure?

No — IVF outcomes depend on many factors, not just sperm shape. Egg quality, embryo development, and the health of the uterus all play a major role. Teratozoospermia may contribute, but it is rarely the only reason a cycle doesn’t succeed. [48]

ICSI (Intracytoplasmic sperm injection)

ICSI is often suggested when sperm morphology is very poor, as it bypasses natural fertilisation by allowing an embryologist to inject a single healthy-looking sperm directly into the egg. This can be especially helpful in severe male factor cases.

However, research shows that for isolated teratozoospermia — when only shape is affected but count and motility are normal — ICSI doesn’t always improve outcomes compared to IVF. Studies have found similar fertilisation, pregnancy, and live birth rates, with no added risk to babies. [47,49,50]

Clinics may still recommend ICSI if there has been a previous IVF failure or if multiple sperm parameters are affected, but sperm shape alone isn’t always a reason to skip IVF.

Sperm freezing

Men with teratozoospermia can freeze sperm for future use, and IVF with frozen sperm is generally just as successful as with fresh. The sample is mixed with a protective fluid, divided into small “straws,” and stored in liquid nitrogen, so not all sperm need to be thawed at once. [51]

Research from a small study shows that abnormally shaped sperm may be more vulnerable to DNA damage during freezing, suggesting around three times more damage compared to normal sperm. Even so, enough healthy sperm usually survive for treatment, and techniques like ICSI allow embryologists to select the best sperm available. [52]

Summary

Teratozoospermia can feel like a daunting diagnosis, but it doesn’t mean parenthood is off the table. Many men with low sperm morphology still conceive naturally, and for those who need help, fertility treatments like IUI, IVF, or ICSI offer proven routes forward. What matters most is looking at the bigger picture — sperm count, motility, DNA quality, and the fertility health of both partners.

If you’ve been told you have teratozoospermia, try to see it as one piece of the puzzle rather than the whole story. With the right support, tailored treatment, and often a few lifestyle changes, chances of pregnancy remain very possible. If you’re unsure about next steps, your GP or fertility specialist can guide you through options and help find the approach that best fits your situation.

Ready to take the next step? Use our Clinic Match tool to explore fertility clinics and find the right fit for your journey.

Teratozoospermia FAQs

Is teratozoospermia a genetic problem?

Sometimes. Most cases of teratozoospermia are linked to lifestyle or medical factors, but certain rare, severe forms — such as globozoospermia (round-headed sperm) or macrozoospermia (large-headed sperm) — are caused by specific gene mutations. These genetic forms account for only a small proportion of cases, but when present, they can significantly impact fertility and may prompt genetic counselling and tailored treatment. [53,54,55]

How many men suffer from teratozoospermia?

There isn’t a clear number, because large-scale population studies on sperm morphology are limited. One review estimates that around 4% of infertile men have isolated teratozoospermia when using strict criteria (<5% normal forms). But because definitions of “normal” vary between labs and studies, the true prevalence is likely higher — and many cases may go undiagnosed until fertility testing. [56]

How serious is teratozoospermia?

On its own, teratozoospermia isn’t always as serious as it sounds. Some men with very low morphology percentages still conceive naturally, while others may need support through treatments like IUI, IVF, or ICSI. What really matters is how sperm shape looks alongside other factors such as count, motility, DNA quality, and the fertility health of the female partner. In severe cases, it can make conception more difficult, but it rarely rules it out completely.

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