Semen analysis is the cornerstone of male fertility evaluation with WHO guidelines providing the basis for procedural standardization and quality control worldwide.[1] However, after its publication, the 5th Edition was criticized for suggesting reference ranges of semen parameters as the mainstay in the evaluation of the male fertility potential.[1] At this stage, generally accepted cut-off values for reproductive outcomes are still lacking.[1]

The minimum reference limits for semen parameters are based on data from fertile men and are intended to guide clinical interpretation. "Semen parameter values falling above or below the lower limit do not by themselves predict either fertility or infertility." With the exception of the aforementioned anomalies (which clearly cause infertility), "none of the individual sperm parameters (e.g., concentration, morphology, motility) are highly predictive of fertility or diagnostic of infertility."

The sixth edition of the WHO Manual for the Laboratory Examination and Processing of Human Semen is a reference document for procedures and methods for the laboratory examination and processing of human semen, which are intended to maintain and sustain the quality of analysis and the comparability of results from different laboratories.[6] Semen analysis may be useful in both clinical and research settings, for investigating male fertility status as well as monitoring spermatogenesis during and following gonadotoxic therapies.[6] Reference limits are based on the semen characteristics of men whose partners had a time-to-pregnancy of 12 months or less; they do not define fertile or infertile status on their own.[6]

Impaired semen parameters alone cannot be used to predict fertility as these men still have a chance of being fertile, except when a man has azoospermia, necrospermia or globozoospermia.[2] Men with these findings on semen analysis are guaranteed to be infertile, and they are the only cases in which semen analyses can predict infertility with absolute certainty.[2] Studies have shown that the total motile sperm count (volume × concentration × motility) has been the most predictive factor in determining fertility compared to volume, concentration, and motility individually, but even this does not perfectly separate fertile from infertile men.[2]

Worldwide data have established semen analysis reference values based upon semen samples obtained from men whose partners were pregnant within one year of unprotected intercourse. However, semen analysis is a poor predictor of fertility because the methodology is not standardized and sperm functional defects cannot be measured. Men may be infertile with normal semen analyses and conversely fertile with abnormal semen analyses.

The 2010 WHO sperm reference values for these parameters were as follows: a semen volume of 1.5 mL, sperm concentration of 15 million/mL, sperm total motility of 40%, and sperm progressive motility of 32%.[2] The 2021 WHO sperm reference values for these parameters are a semen volume of 1.4 mL, sperm concentration of 16 million/mL, sperm total motility of 42%, and sperm progressive motility of 30%.[2] Health professionals related to infertility treatment should know that the new reference limits were defined as a result of the new manual’s methodology and the men should not be classified as fertile or infertile based on only semen analysis.[2]

A conventional semen analysis cannot reliably predict the chance of pregnancy or differentiate fertile vs. infertile men (except in the most extreme cases).[9] Normozoospermia is commonly defined as having semen parameters ≥15 million sperm/mL, ≥40% overall motility, and ≥4% normal morphology.[8] Nonetheless, studies summarized in this review show poor discrimination: men with normal semen parameters may still be infertile, and men with abnormal parameters may still achieve pregnancy.[9]

The WHO has provided normal reference limits for semen analysis.[5] The following values represent the accepted 5th percentile for the measured parameters: Volume: >1.5 mL; Total sperm number: 39 million sperm per ejaculate or more; Morphology: >4% normal forms; Progressive motility: >32%.[5] It is important to recognize that these values represent lower reference limits and that semen analysis alone cannot diagnose or exclude male infertility; clinical correlation and female partner factors must be considered.[5]

In contrast, when a man is infertile with a normal semen analysis and workup, the term “unexplained infertility” is used (presuming there is not any identifiable female-factor cause). It is hypothesized that genetic defects (either not yet identified or unable to be tested for) underlie unexplained infertility in some patients. Despite these limitations, [semen analysis] is still the single best test we have when evaluating these patients.

It is important to note that a normal semen analysis does not guarantee fertility, and an abnormal analysis does not necessarily mean infertility. For normal conception, a man must have sperm cells that are functionally able to fertilize eggs. Indeed, male factor infertility can be present even in the setting of a normal sperm count.

Many people with low sperm counts are able to get their partners pregnant. Likewise, some people with typical sperm counts are not able to start pregnancies. Even if you have enough sperm, other factors are important to start a pregnancy. These factors include healthy sperm movement, also called motility.

The new criteria establish “clinical reference ranges” for sperm count (concentration), motility, and morphology to help classify men as fertile or sub-fertile.[3] Although each sperm parameter could predict fertility and subfertility, none was a powerful discriminator.[3] It is important to emphasize that normal reference values for semen parameters do not reflect normal sperm concentration in the general population, nor do they equate with the minimum values required for conception; men with semen variables outside the reference ranges may be fertile and, conversely, men having values within the reference range still may be infertile.[3]

Semen analysis testing is not a perfect predictor of male fertility potential, but it is the best overall general test that we have available at this point in time.[4] The author argues that a better definition of male fertility potential would use stricter cutoffs for total motile count and other parameters, yet still notes that numbers and quality of sperm are only the strongest predictors we currently have, not absolute determinants of fertility.[4] The discussion stresses that semen analysis must be combined with clinical history and female partner factors when assessing a couple’s fertility.[4]

A normal sperm count is roughly 15 million or more sperm per milliliter of semen. These numbers are statistical benchmarks based on fertile men, so falling below these ranges can indicate a potential issue with fertility. “Normal” ranges are not strict pass/fail criteria. Many men with somewhat lower values can still father children; they just have a lower probability per cycle, and likewise, some men with excellent numbers may still encounter fertility difficulties due to other factors.

The sixth edition addresses this by providing more comprehensive reference limits for both fertility and infertility.[9] However, WHO reference limits are derived from men whose partners conceived within 12 months, and they represent statistical lower limits rather than strict thresholds for the ability to achieve pregnancy.[9] Semen analysis remains a useful but imperfect tool: normal semen parameters do not guarantee fertility, and abnormal parameters do not necessarily indicate sterility.[9]

In WHO 2010, the new normal values are based on data from men with proven fertility, men who were known to help their partners conceive in the previous 12 months.[5] Based on our experience, concentration and progressive motility are the most important sperm parameters in predicting the likelihood of pregnancy via coitus or intrauterine insemination.[5] For example, when sperm concentration is < 10 million/ml and/or progressive motility < 20%, the chance of pregnancy using the conventional methods is very low, but not necessarily zero; in vitro fertilization would provide the best chance of pregnancy.[5]

Healthline explains that semen tests analyze sperm count, shape, and motility to test for infertility related to sperm production. It notes that a healthy sperm count is often necessary for natural conception and that lower counts or poor quality reduce the chance of pregnancy each month. However, the article acknowledges that many factors can affect fertility, including lifestyle and underlying medical conditions, and implies that semen analysis is only one part of evaluating male fertility, not a definitive test of whether a man is fertile or infertile.

Abnormal results may suggest a male infertility problem. For example, if the sperm count is very low or very high, a man may be less fertile. An abnormal result does not always mean there is a problem with a man's ability to have children. Therefore, it is not completely clear how the test results should be interpreted.

A total motile count of over 20 million is considered normal. However, even if you have more than 20 million motile sperm, it may not result in a higher chance of pregnancy. If you have fewer than 20 million motile sperm, your chances of having a successful pregnancy go down. Even if you have no sperm in your ejaculate, this doesn’t mean you’ll never be able to have a child.

According to the World Health Organization’s laboratory manual for human semen analysis, core parameters such as volume, concentration, total sperm count, motility, and morphology each have established reference ranges that help clinicians understand how well sperm are produced, how they move, and how they function.[4] Normal results include volume above 1.5 mL, concentration of at least 15 million/mL, motility of 40% or more, and morphology of 4% or higher.[4] Do all numbers need to be normal for fertility? No. Many men with one or two borderline parameters still conceive naturally, depending on the whole pattern of results.[4]

Below-average results on a semen analysis report do not necessarily guarantee a person will struggle with infertility. An abnormal result does not always mean infertility. However, if the sperm count is very low or very high, a man may be less fertile. To investigate fertility issues, a doctor typically recommends a sperm analysis, a specialized test examining sperm health.

Low sperm count is when there's a low amount of sperm in your semen. It can make it harder for you and your partner to get pregnant (conceive), but it may still be possible to conceive naturally and there are fertility treatments that can help. The main test to check for low sperm count is a semen analysis test.

This clinic’s FAQ on semen analysis states: "It’s important to know that one semen analysis alone doesn’t tell you everything about whether or not you’ll be able to get pregnant or not." It adds that even clearly abnormal parameters (such as zero sperm or less than a million sperm) are more predictive, whereas modest abnormalities are common and do not necessarily predict reproductive potential. They emphasize that morphology thresholds (e.g., 4% normal forms) are "not been shown to be very predictive of whether somebody will get pregnant or not," underscoring the broader limitation that normal or near‑normal semen analysis is not sufficient to guarantee fertility.

This explanatory article notes that semen analysis results point to problems with male fertility and that deficiencies revealed in a sample may prevent fertilization or reduce the probability of pregnancy. It implicitly treats semen analysis as a probabilistic indicator: abnormalities usually reduce the likelihood of pregnancy rather than absolutely determine infertility, and conversely, normal results increase, but do not ensure, the probability of natural conception.

Semen analysis provides information about semen volume, sperm concentration, morphology, motility and other characteristics, but it does not assess all aspects of sperm function such as DNA integrity, capacitation, or ability to penetrate the egg. Men with normal semen parameters can still be infertile due to functional sperm defects or non-sperm-related male factors (e.g., erectile or ejaculatory dysfunction), while some men with abnormal parameters achieve pregnancy without assisted reproduction.