MALE FERTILITY • SEMEN ANALYSIS • BRISBANE
Low Sperm Count, Motility & Morphology: Understanding OAT
Oligoasthenoteratozoospermia — often shortened to OAT or OATS — means that sperm concentration, sperm motility and sperm morphology are all below their laboratory reference ranges.
Because several semen parameters are affected at the same time, OAT can represent a more significant male-factor fertility pattern than an isolated abnormality. It still does not, by itself, diagnose the cause of infertility or determine which fertility treatment is appropriate.
Educational information only. A semen analysis cannot by itself determine whether a man is fertile or infertile or predict an individual couple's chance of pregnancy.
UNDERSTANDING THE TERM
What is oligoasthenoteratozoospermia?
OAT describes a semen-analysis pattern in which three abnormalities occur together: sperm concentration is reduced, sperm motility is reduced and the proportion of sperm meeting strict morphology criteria is reduced.
It is therefore different from isolated oligozoospermia, isolated asthenozoospermia or isolated teratozoospermia. When several semen parameters are abnormal together, there may be fewer sperm available, fewer progressing effectively and fewer meeting strict laboratory morphology criteria.
The term describes what the semen analysis looks like. It does not tell us why the abnormalities are present. The next step is usually to confirm the result and assess whether there is an identifiable male reproductive factor.
HOW THE REPORT IS CLASSIFIED
What numbers are commonly used as reference limits?
Current WHO-derived reference data used in European guidance list the following lower reference limits. They are population-based reference values rather than pass-or-fail fertility thresholds.
Sperm concentration
Approximately 16 million sperm/mL is the lower reference limit for sperm concentration.
Progressive motility
Approximately 30% is the lower reference limit for progressive sperm motility.
Total motility
Approximately 42% is the lower reference limit for total motility, including progressive and non-progressive sperm.
Normal morphology
Approximately 4% normal forms is the lower reference limit when strict morphology criteria are applied.
SEVERITY MATTERS
Mild OAT and severe OAT are not the same clinical situation
A semen analysis that sits just below the reference range for count, motility and morphology can have different implications from a sample with a very low sperm concentration, markedly reduced progressive motility and severely abnormal morphology.
In particular, severe oligozoospermia can be associated with a higher likelihood of certain genetic abnormalities and other important male-factor causes. The lower the sperm concentration, the more important it becomes to assess whether specific hormonal or genetic investigations are indicated.
This is one reason that the label “OAT” is less useful than the actual numbers. Two men can both have OAT but have substantially different fertility implications and different investigation pathways.
WHY OAT DESERVES ASSESSMENT
Several parts of sperm production or function are abnormal at once
There are fewer sperm available
Reduced sperm concentration lowers the number of sperm present in the ejaculate before motility and morphology are considered.
Fewer sperm may move effectively
Reduced progressive motility can further decrease the number of sperm capable of moving effectively through the reproductive tract under natural conditions.
Morphology is abnormal as well
A lower proportion of sperm meet strict laboratory criteria for normal shape, although morphology alone does not determine fertilising ability.
The combined pattern may point to impaired spermatogenesis
When several semen parameters are abnormal together, assessment often focuses on whether sperm production within the testes is impaired.
There may be a clinically relevant contributor
Examination, history and selected investigations may identify a reproductive, hormonal, genetic or general health factor that deserves attention.
The female partner's fertility factors still matter
The appropriate timing and fertility pathway depend on both partners rather than the semen-analysis result in isolation.
POSSIBLE CONTRIBUTORS
What can cause OAT?
OAT is not one disease and does not have one universal cause. Some men have an identifiable contributor, while in others the cause remains unexplained despite appropriate assessment.
MALE FERTILITY ASSESSMENT
What should be checked after an OAT result?
Current male-infertility guidance recommends confirming an abnormal baseline semen analysis and then selecting investigations according to the severity and clinical pattern.
Repeat the semen analysis
Semen parameters vary between samples. When the baseline analysis is abnormal, at least one repeat analysis is usually important before the pattern is considered persistent.
Review the actual numbers, not just the label
Concentration, total sperm number, progressive motility, total motility, morphology, semen volume and laboratory comments should all be reviewed together.
Take a complete reproductive and medical history
Previous fertility, duration of trying, childhood testicular history, surgery, injury, infections, significant illness, exposures and previous fertility treatment can provide important clues.
Perform a male reproductive examination
Testicular size and consistency, the epididymis and vas deferens, and whether a clinical varicocele or another reproductive finding is present can influence the investigation pathway.
Check reproductive hormones when indicated
Hormonal assessment is particularly relevant when sperm concentration is reduced and can help distinguish some forms of impaired testicular sperm production from endocrine causes.
Consider genetic testing in severe low-count patterns
When sperm concentration is very low, chromosome testing, Y-chromosome testing and genetic counselling may be appropriate depending on the measured concentration and clinical findings.
Use imaging selectively
Scrotal ultrasound or other imaging is used when there is a relevant clinical indication rather than automatically for every man with OAT.
Assess both partners in parallel
Female age, ovarian reserve, tubal factors, reproductive history and duration of infertility can materially influence how quickly fertility treatment should be considered.
HAVE YOUR SEMEN REPORT?
Put count, motility and morphology together
The Semen Analysis Interpreter helps review sperm concentration, progressive motility, morphology, volume and other semen parameters in one place.
FERTILITY PLANNING
What does OAT mean for fertility?
OAT can reduce the probability of natural conception, particularly when the abnormalities are severe. It does not, however, determine a single treatment pathway.
Natural conception may still occur
OAT does not mean natural conception is impossible. The likelihood for an individual couple depends on the severity of the semen abnormality and multiple female and male factors.
Severity influences timing
Mild abnormalities may be approached differently from severe OAT, especially when the female partner is younger and there are no other major fertility factors.
A contributing male factor may be addressed
If assessment identifies a clinically relevant and potentially modifiable contributor, its significance and available management options can be discussed individually.
IUI suitability depends on more than the diagnosis
Whether intrauterine insemination is reasonable depends on the total number of motile sperm, the processed sample and the couple's wider fertility assessment rather than the OAT label alone.
IVF or ICSI may be considered in selected couples
Assisted-reproduction decisions depend on the severity of the semen abnormality, female fertility factors, duration of infertility and previous treatment or fertilisation history.
The plan should be coordinated
Male-factor assessment is most useful when integrated with the fertility specialist and reproductive laboratory so that investigations and treatment timing are aligned.
RELATED SEMEN-ANALYSIS PATTERNS
How is OAT different from the other common terms?
Cryptozoospermia
Sperm are present only in extremely small numbers and may only be found after laboratory concentration.
Asthenozoospermia
The main abnormality is reduced sperm motility.
Teratozoospermia
The main abnormality is a low proportion of sperm meeting strict morphology criteria.
OAT / OATS
Count, motility and morphology are all abnormal together.
Azoospermia
No sperm are identified in the ejaculate after appropriate laboratory examination.
Read about azoospermia →A PRACTICAL WAY TO THINK ABOUT OAT
Do not focus on one “bad” number
With OAT, the clinical significance comes from the interaction between several abnormal semen parameters. A concentration of 14 million/mL, progressive motility of 28% and morphology of 3% is technically different from a concentration of 2 million/mL, progressive motility of 10% and morphology of 1%, even though both may be labelled OAT.
The second pattern suggests a much more severe reduction in overall sperm availability and is more likely to trigger a broader male infertility assessment.
The most useful interpretation therefore asks: how severe is the overall semen abnormality, is it persistent, is there a likely cause, and how does it fit with the couple's reproductive timeline?
RELATED MALE FERTILITY INFORMATION
Explore the wider male fertility pathway
MALE REPRODUCTIVE UROLOGY
Individual assessment of combined semen abnormalities
Dr Jack Crozier is a FRACS-qualified Brisbane urologist with advanced fellowship training in andrology. His practice includes male infertility, abnormal semen analysis, azoospermia, varicocele and microsurgical reproductive urology.
Assessment of OAT focuses on confirming the semen pattern, establishing how severe it is, identifying whether there is an underlying male reproductive factor and coordinating the male assessment with the couple's wider fertility plan.
FREQUENTLY ASKED QUESTIONS
OAT / oligoasthenoteratozoospermia FAQs
What does OAT mean on a semen analysis?
OAT stands for oligoasthenoteratozoospermia. It means sperm concentration is low, sperm motility is reduced and sperm morphology is below the laboratory reference range.
Is OAT the same as OATS?
The terms OAT and OATS are both used to describe the same combined semen-analysis pattern. The extra “S” is sometimes used for “syndrome”, but the underlying meaning is the same.
Is OAT severe male infertility?
Not necessarily. OAT ranges from mild abnormalities just below the reference limits to severe abnormalities involving a very low sperm concentration and markedly reduced motility. The actual numbers are more important than the label alone.
Can natural conception occur with OAT?
Yes, natural conception can occur in some couples with OAT. The likelihood depends on the severity of the semen abnormalities, duration of infertility and the reproductive factors of both partners.
Can OAT improve?
That depends on the cause. Semen results can vary, some temporary influences can resolve, and selected men may have an identifiable contributing factor. Other men have persistent impairment of sperm production despite appropriate assessment.
Should an OAT semen analysis be repeated?
Usually yes when the initial result is abnormal. Current male-infertility guidance recommends at least two semen analyses when the baseline analysis is abnormal because semen parameters vary between samples.
Do I need hormone tests?
Hormonal assessment is commonly considered when sperm concentration is reduced, particularly when oligozoospermia is significant. The appropriate tests depend on the history, examination and semen results.
Do I need genetic testing?
Genetic testing becomes more relevant when sperm concentration is very low. Whether chromosome testing, Y-chromosome testing or genetic counselling is appropriate depends on the severity of the sperm-count abnormality and other clinical findings.
Can a varicocele cause OAT?
A clinical varicocele can be associated with reduced sperm concentration and abnormalities in motility or morphology, but finding a varicocele does not prove it is the cause. Its significance is assessed in the context of the full male and couple fertility picture.
Does OAT mean we need IVF or ICSI?
No. OAT does not automatically determine fertility treatment. The decision between continued natural attempts, IUI, IVF, ICSI or another pathway depends on the severity of the semen abnormality, both partners' fertility assessments, reproductive timing and previous treatment history where relevant.
Should I take supplements for OAT?
It is better not to assume that a particular product will correct OAT. Evidence for many products marketed for male fertility is uncertain, and products can have side effects or interactions. Discuss any medicines or supplements you are using or considering with your treating clinician.
When should I see a male fertility specialist?
Review is particularly useful when OAT is confirmed on repeat testing, sperm concentration is very low, infertility has been prolonged, there has been previous fertility-treatment difficulty, or there are relevant testicular, hormonal, genetic or reproductive-history concerns.
MALE FERTILITY ASSESSMENT
Has your semen analysis shown low count, motility and morphology?
An individual male fertility assessment can confirm whether the OAT pattern is persistent, establish its severity, investigate possible contributing factors and help clarify the reasonable next steps alongside your broader fertility plan.