By SwimScore. Medically reviewed by [reviewer name and credentials to be added before publishing]. Last updated October 8, 2026.
Key Takeaways
Oligozoospermia means a low sperm concentration, asthenozoospermia means low sperm movement, and teratozoospermia means a low share of sperm with a normal shape, and a semen analysis can flag any one of them or all three together (called oligoasthenoteratozoospermia, or OAT).
These labels describe how one sample compares with the fifth percentile of fertile men, which in the WHO 6th Edition (2021) is 16 million sperm per mL, 30% progressive motility, 42% total motility, and 4% normal forms, and the authors of that data state that these values are not a dividing line between fertile and subfertile men (Campbell et al., Andrology, 2021).
SwimScore Complete reports concentration, progressive motility, total motility, morphology, and DNA Fragmentation Index (DFI) from a CLIA-certified lab, so a man can see which of these labels actually applies to him and bring the full pattern to a clinician.
Most men first meet these words on a lab report or in a clinic note: oligozoospermia, asthenozoospermia, teratozoospermia. They sound like three different diseases. They are not diseases at all. They are three labels for three ways a single semen sample can fall below a reference number, and the same man can carry one, two, or all three at once. This article explains what each label means in plain English, how much weight the label deserves, and where the research says the label is less useful than the clinic paperwork makes it sound.
What do oligozoospermia, asthenozoospermia, and teratozoospermia mean?
Oligozoospermia is a sperm concentration below the reference value, asthenozoospermia is too few sperm moving well, and teratozoospermia is too few sperm with a normal shape. Each name is Greek in origin and each describes one feature of a sperm sample.
Oligozoospermia means "few sperm." It refers to concentration, the number of sperm in each milliliter of semen. Asthenozoospermia means "weak sperm." It refers to motility, the share of sperm that swim, and especially progressive motility, the share that swim forward in a fairly straight line rather than in circles or twitching in place. Teratozoospermia means "misshapen sperm." It refers to morphology, the share of sperm that look normal under the microscope when the lab applies strict criteria for head, midpiece, and tail shape. Azoospermia, covered in our article on obstructive versus non-obstructive azoospermia, is the most severe end of the same family: no sperm at all.
When more than one parameter is low, the labels combine. Oligoasthenozoospermia means low concentration and low motility. Oligoasthenoteratozoospermia, usually shortened to OAT, means all three are low. Clinicians use these combinations as shorthand, and you will see them on referral letters.
What numbers decide which label a man gets?
The labels depend on cutoffs taken from the bottom edge of what fertile men produce. The WHO 6th Edition (2021) lower reference values come from an analysis of more than 3,500 men in twelve countries whose partners had conceived, and the fifth percentile values in that analysis were a sperm concentration of 16 million per mL, 30% progressive motility, 42% total motility, and 4% normal forms (Campbell et al., Andrology, 2021, doi:10.1111/andr.12983). The same review of the 6th Edition lists a lower value for total sperm number of 39 million per ejaculate (Boitrelle et al., Life, 2021, PMC8706130). SwimScore measures against these WHO 6th Edition values.
"Fifth percentile" means that if you lined up a hundred fertile men by sperm count, the fifth man from the bottom sits at this number. Five out of every hundred men who fathered a child had a result below it. That tells you something important about what the cutoff is not: it is not the point where fertility ends. The authors of the 2021 analysis say plainly that these values do not represent distinct limits between fertile and subfertile men (Campbell et al., Andrology, 2021).
One more detail matters for anyone reading older paperwork. The WHO 6th Edition manual voluntarily removed terms such as asthenozoospermia and teratozoospermia and moved toward describing results in numbers (Boitrelle et al., Life, 2021). The labels remain in everyday clinical use, which is why this article explains them, but a lab report built on the newest manual may simply show the values without a label.
What causes each pattern?
Each pattern has several possible causes, and the label alone does not tell you which one applies. Low concentration can come from a problem with the signals that tell the testes to make sperm, a problem inside the testes, or a blockage, and it is often linked to conditions we cover separately, such as varicocele (enlarged veins around the testicle that can raise local temperature), hormone problems, and past testosterone therapy. Low motility is commonly associated with heat, infection or inflammation, varicocele, and oxidative stress (damage caused by unstable molecules called free radicals), and it can also reflect how long the sample sat before it reached the lab. Low normal-form percentage is the least specific of the three, because shape varies widely even in fertile men and the result depends heavily on how carefully the lab scores it.
The hormone panel is often the first step in telling these causes apart. FSH and LH are the two signals the pituitary gland sends to the testes, and testosterone is what the testes produce in response. Reading them together points toward either a signaling problem or a testicle problem, which we explain in what your FSH level is telling you and low testosterone with high LH versus normal LH. A semen label with no hormone context leaves out half the picture.
How much does the label predict about the chance of a pregnancy?
Less than most men expect. The clearest evidence is a Dutch cohort study of 1,177 couples with either male-factor or unexplained infertility, followed for three years. Every WHO-defined abnormal group had a lower rate of spontaneous ongoing pregnancy than the unexplained group (odds ratios between 0.136 and 0.397). But when the abnormal groups were compared with each other, there were no significant differences in most pairings. The exceptions were that OAT did worse than asthenozoospermia alone or teratozoospermia alone, and oligoasthenozoospermia did worse than asthenozoospermia alone (Hamilton et al., Human Reproduction, 2015, doi:10.1093/humrep/dev058). In plain terms, the specific name mattered far less than whether more than one parameter was low.
The same study found that a number combining the three parameters did a better job. Total motile sperm count, or TMSC, multiplies semen volume by sperm concentration by the share of sperm that are moving. Couples with a TMSC under 1 million or between 1 and 5 million had significantly lower spontaneous pregnancy rates than couples with a TMSC between 5 and 10 million. The authors suggested three rough prognostic groups: under 5 million, between 5 and 20 million, and above 20 million, and recommended TMSC over the WHO labels for describing severity (Hamilton et al., Human Reproduction, 2015). We cover that number in detail in our TMSC article. A caution: this was a cohort study at three Dutch hospitals, couples were not censored when treatment started, and the outcome included pregnancies that followed treatment, so it describes prognosis rather than proving that a TMSC band causes a given result.
An older and larger study points the same way about thresholds in general. In the National Cooperative Reproductive Medicine Network study, researchers compared 765 infertile couples with 696 fertile couples at nine sites. They found a concentration under 13.5 million per mL, motility under 32%, and strict-criteria normal forms under 9% were in the subfertile range, and concentration over 48 million per mL, motility over 63%, and normal forms over 12% were in the fertile range, with an "indeterminate" zone in between. There was extensive overlap between fertile and infertile men for all three measures, and none was a powerful discriminator, with morphology the strongest (Guzick et al., New England Journal of Medicine, 2001, doi:10.1056/NEJMoa003005). That study used older methods and different morphology cutoffs than the WHO 6th Edition, so the numbers should not be swapped into a modern report. The lesson that carries over is the overlap: a man below a cutoff is not necessarily infertile, and a man above it is not guaranteed to conceive.
What are we more skeptical about?
We are skeptical of three things. The first is treating the label as a diagnosis. Oligozoospermia, asthenozoospermia, and teratozoospermia describe a result, not a cause, and the Dutch data above show the individual name predicts little beyond how many parameters are off. The second is any single-parameter "fix," including the idea that a supplement aimed at one label will resolve it. The largest recent review of supplement trials pooled 50 randomized trials, each lasting at least 12 weeks, and found no effect of any dietary supplement on pregnancy or live birth. Some supplements improved single sperm parameters in some analyses, for example zinc and folic acid for concentration, and selenium, carnitine, and CoQ10 for motility, but the certainty of that evidence was generally low or very low and most trials had concerns about bias (Michaelsen et al., Nutrients, 2025, doi:10.3390/nu17101710). We walk through the individual parameter evidence in our concentration article, our motility article, and our morphology article.
The third is the false precision of a single sample. Semen quality varies from one collection to the next, so one flagged result is a reason to look closer, not a conclusion. A repeat sample is standard practice before anyone draws a firm line.
What should a man with one of these labels do next?
The practical path starts with knowing which parameters are off and by how much, then looking for a cause. Repeat the semen analysis to confirm the pattern. Check the hormone panel, because hormone problems and past or current testosterone use are among the most common reversible causes. Ask a urologist to examine for a varicocele, since that is a correctable finding. Look at DNA fragmentation as well, because two men with the same label can have very different DNA quality, as we explain in our DNA fragmentation article. If a lifestyle change or treatment is started, sperm take roughly 72 days to develop, so give it at least 12 weeks before retesting.
SwimScore Complete combines a CLIA-certified semen analysis (concentration, progressive motility, total motility, morphology), DNA fragmentation testing, and a hormone panel, so a man can see his full pattern in one report and tell a clinician exactly which parameters are low. You can learn more about SwimScore Complete here. Clinics that want a standardized male-factor report for their patients can see how it works on our for clinics page.
Our Take
We know that these three labels are shorthand for three measurements, that they are defined by the bottom edge of fertile men and not by a line between fertile and infertile, and that having more than one of them low carries a worse prognosis than having just one. We know the newest WHO manual has moved away from the labels themselves.
We do not know that any single label tells a man what to do, and we do not have good evidence that a supplement aimed at a label changes the chance of a baby. Those are real gaps, and anyone selling a fix for "your oligozoospermia" is getting ahead of the data.
It is still worth acting, because the numbers behind the label are measurable and the common causes are findable. Know the values. Look for the cause with a hormone panel and a physical exam. Give any change at least 12 weeks. Measure again.
Frequently Asked Questions
What is the difference between oligozoospermia, asthenozoospermia, and teratozoospermia?
Oligozoospermia is a low sperm concentration, asthenozoospermia is low sperm movement, and teratozoospermia is a low share of normally shaped sperm. They describe three different measurements on the same semen sample, and more than one can be present at once.
What is oligoasthenoteratozoospermia (OAT)?
Oligoasthenoteratozoospermia, or OAT, means concentration, motility, and the share of normal-shaped sperm are all below the reference values. In a Dutch cohort of 1,177 couples, OAT had lower spontaneous pregnancy rates than asthenozoospermia alone or teratozoospermia alone (Hamilton et al., Human Reproduction, 2015).
What are the WHO 6th Edition cutoffs for these conditions?
The WHO 6th Edition (2021) fifth percentile values are 16 million sperm per mL, 30% progressive motility, 42% total motility, and 4% normal forms (Campbell et al., Andrology, 2021). The authors state these are not distinct limits between fertile and subfertile men.
Can I still get my partner pregnant with one of these diagnoses?
Yes, many couples do. Men below a cutoff and men above it overlap heavily in fertility, and none of the three parameters is diagnostic of infertility on its own (Guzick et al., New England Journal of Medicine, 2001).
Do supplements fix low count, motility, or morphology?
Not reliably. A 2025 meta-analysis of 50 randomized trials found no effect of dietary supplements on pregnancy or live birth, and certainty for the small improvements in single parameters was generally low or very low (Michaelsen et al., Nutrients, 2025).
References
1. Campbell MJ, Lotti F, Baldi E, et al. Distribution of semen examination results 2020: a follow up of data collated for the WHO semen analysis manual 2010. Andrology, 2021;9(3):817-822. doi:10.1111/andr.12983
2. Boitrelle F, Shah R, Saleh R, et al. The sixth edition of the WHO manual for human semen analysis: a critical review and SWOT analysis. Life, 2021;11(12):1368. PMC8706130
3. Hamilton JA, Cissen M, Brandes M, et al. Total motile sperm count: a better indicator for the severity of male factor infertility than the WHO sperm classification system. Human Reproduction, 2015;30(5):1110-1121. doi:10.1093/humrep/dev058
4. Guzick DS, Overstreet JW, Factor-Litvak P, et al. Sperm morphology, motility, and concentration in fertile and infertile men. New England Journal of Medicine, 2001;345(19):1388-1393. doi:10.1056/NEJMoa003005
5. Michaelsen MP, Poulsen M, Bjerregaard AA, et al. The effect of dietary supplements on male infertility in terms of pregnancy, live birth, and sperm parameters: a systematic review and meta-analysis. Nutrients, 2025;17(10):1710. doi:10.3390/nu17101710
This is general education and not medical advice. An abnormal semen analysis should be evaluated by a urologist or andrologist.
SwimScore uses CLIA-certified labs for all semen analysis and hormone testing, assessed against WHO 6th Edition clinical thresholds.
