What is a Semen Analysis?
A semen analysis (also called a seminogram or spermogram) is the cornerstone laboratory test for evaluating male fertility. It assesses the characteristics of a man's semen and the sperm it contains. Male factor infertility contributes to approximately 40–50% of all infertility cases, making semen analysis an essential component of any fertility workup.
The test evaluates both macroscopic properties (volume, appearance, viscosity, liquefaction time, pH) and microscopic parameters (sperm concentration, motility, morphology, vitality). Results are compared against reference values established by the World Health Organization (WHO), which published its most recent 6th edition laboratory manual in 2021.
WHO 2021 Reference Values
The WHO reference values represent the 5th percentile of fertile men — meaning 95% of men who achieved a pregnancy within 12 months had values at or above these thresholds. Values below these references do not mean a man is infertile, but suggest reduced fertility potential.
| Parameter | WHO 2021 Reference (5th percentile) | Unit |
|---|---|---|
| Ejaculate Volume | ≥1.4 | mL |
| Sperm Concentration | ≥16 | million/mL |
| Total Sperm Count | ≥39 | million per ejaculate |
| Total Motility | ≥42% | % motile |
| Progressive Motility | ≥30% | % progressive |
| Vitality | ≥54% | % live |
| Normal Morphology | ≥4% | % normal forms (strict criteria) |
Important: These are lower reference limits, not "ideal" values. Most fertile men have values well above these thresholds. A single abnormal result should be confirmed with a repeat test after 2–3 months, as semen parameters can vary significantly between samples.
Understanding Each Parameter
Ejaculate Volume
Normal ejaculate volume is 1.4 mL or greater. Low volume (hypospermia) may indicate incomplete collection, retrograde ejaculation, ejaculatory duct obstruction, hypogonadism, or absence of seminal vesicles. Very low volume can significantly reduce total sperm count even if concentration is normal.
Sperm Concentration
Sperm concentration measures the number of sperm per milliliter of semen. The WHO 2021 reference is 16 million/mL or greater. Low concentration (oligozoospermia) is classified as mild (10–15 M/mL), moderate (5–10 M/mL), or severe (<5 M/mL). Complete absence of sperm is termed azoospermia.
Total Motility
Total motility represents the percentage of sperm that show any form of movement, including progressive (forward) and non-progressive (in-place) motility. The reference value is 42% or greater. Reduced motility is called asthenozoospermia.
Progressive Motility
Progressive motility measures sperm that move forward in a straight line or in large circles. Only progressively motile sperm can traverse the female reproductive tract to reach and fertilize the egg. The reference value is 30% or greater.
Vitality
Vitality measures the percentage of live (viable) sperm in the sample, assessed using dye exclusion or hypo-osmotic swelling tests. It is particularly important when motility is low, as it helps distinguish between dead sperm (necrozoospermia) and live but immotile sperm. The reference value is 54% or greater.
Normal Morphology
Morphology assesses the shape and structure of sperm using strict (Tygerberg) criteria. Only sperm with a normal oval head, intact midpiece, and uncoiled tail are counted as normal. The reference is 4% or greater — this seemingly low number reflects the strict criteria used. Reduced morphology is called teratozoospermia.
Functional Sperm Count
The functional sperm count estimates the number of sperm that are simultaneously alive, motile, and morphologically normal — the ones most likely to achieve fertilization naturally:
This calculation provides a more comprehensive assessment of fertility potential than any single parameter alone. A man may have adequate concentration but poor motility and morphology, resulting in a low functional sperm count.
Semen Analysis Terminology
| Term | Definition |
|---|---|
| Normozoospermia | All parameters within normal reference ranges |
| Oligozoospermia | Sperm concentration below reference (<16 M/mL) |
| Asthenozoospermia | Motility below reference (<42% total or <30% progressive) |
| Teratozoospermia | Normal morphology below reference (<4%) |
| Oligoasthenoteratozoospermia (OAT) | All three parameters abnormal — most common pattern |
| Azoospermia | Complete absence of sperm in the ejaculate |
| Cryptozoospermia | Sperm found only after centrifugation of the sample |
| Necrozoospermia | High percentage of dead sperm; low vitality |
| Aspermia | Complete absence of ejaculate |
| Hypospermia | Ejaculate volume below reference (<1.4 mL) |
Factors Affecting Male Fertility
Modifiable Factors
- Heat exposure: Hot tubs, saunas, tight underwear, laptop use on lap — scrotal temperature elevation impairs spermatogenesis
- Smoking: Reduces concentration, motility, and morphology; increases DNA fragmentation
- Alcohol: Heavy consumption lowers testosterone and impairs sperm production
- Obesity: Alters hormone levels (increased estrogen, decreased testosterone); associated with poorer semen parameters
- Medications: Testosterone supplementation (paradoxically suppresses sperm production), anabolic steroids, chemotherapy, some antidepressants, calcium channel blockers
- Stress: Chronic stress affects hormonal balance and semen quality
- Diet: Antioxidant-rich diets (fruits, vegetables, nuts, fish) associated with better semen parameters
Non-Modifiable Factors
- Age: Sperm quality declines gradually after age 40, with increased DNA fragmentation
- Genetics: Y-chromosome microdeletions, Klinefelter syndrome, cystic fibrosis gene mutations
- Varicocele: Present in 15% of men and 40% of infertile men; the most common correctable cause of male infertility
- Cryptorchidism: History of undescended testes, even if corrected surgically
- Infections: Past mumps orchitis, sexually transmitted infections
Preparing for a Semen Analysis
Proper sample collection is essential for accurate results:
- Abstinence period: 2–7 days of sexual abstinence (WHO recommends 2–7 days; most labs prefer 2–5 days)
- Collection method: Masturbation into a sterile, wide-mouthed container provided by the laboratory
- Complete collection: The first portion of the ejaculate is the most sperm-rich; losing it significantly affects results
- Temperature: Keep the sample at body temperature during transport (within clothing, close to the body)
- Timing: Deliver the sample to the laboratory within 30–60 minutes of collection
- Avoid: Lubricants (most are spermicidal), condom collection (unless special non-toxic condoms are used), coitus interruptus
When to See a Specialist
Consider referral to a reproductive urologist or fertility specialist when:
- Two or more semen analyses show abnormal parameters
- Azoospermia or severe oligozoospermia (<5 million/mL) is detected
- The couple has been trying to conceive for 12 months without success (6 months if female partner is over 35)
- There is a history of known risk factors (varicocele, undescended testes, genital surgery, cancer treatment)
- Physical examination reveals abnormalities (small testes, varicocele, absent vas deferens)
- Hormonal evaluation shows abnormal FSH, LH, or testosterone levels
Worked Example
A patient presents with the following semen analysis results:
- Volume: 3.0 mL (Ref: ≥1.4) — Normal
- Concentration: 40 million/mL (Ref: ≥16) — Normal
- Total motility: 50% (Ref: ≥42%) — Normal
- Progressive motility: 35% (Ref: ≥30%) — Normal
- Vitality: 60% (Ref: ≥54%) — Normal
- Normal morphology: 5% (Ref: ≥4%) — Normal
All parameters are within WHO 2021 reference ranges. The total sperm count of 120 million is well above the 39 million threshold. The functional sperm count of 1.8 million represents the estimated number of simultaneously motile, alive, and morphologically normal sperm. This result is consistent with normozoospermia.
Frequently Asked Questions
Can a single semen analysis diagnose infertility?
No. Semen parameters can vary considerably between samples due to abstinence period, illness, stress, and other factors. At least two analyses, performed 2–3 months apart, are recommended before drawing conclusions. Even men with abnormal results may achieve natural conception.
What does a "normal" semen analysis guarantee?
A normal semen analysis does not guarantee fertility. The WHO reference values identify the 5th percentile of fertile men, but semen analysis does not assess sperm DNA integrity, capacitation ability, acrosome function, or the ability to bind and penetrate the egg. Up to 15% of infertile men have normal conventional semen parameters.
How long does sperm production take?
The complete cycle of spermatogenesis takes approximately 72–76 days, with an additional 10–14 days for sperm maturation in the epididymis. This means that any intervention (lifestyle change, medication, surgery) will take about 3 months to be reflected in a semen analysis.
Does morphology of 4% mean 96% of sperm are abnormal?
Yes, under strict (Tygerberg) criteria, only sperm with a perfectly shaped head, midpiece, and tail are considered "normal." This is a very strict assessment, and even fertile men typically have 4–14% normal forms. The correlation between morphology and fertility is well-established but should be interpreted alongside other parameters.
Can lifestyle changes improve semen parameters?
Yes. Quitting smoking, reducing alcohol intake, maintaining a healthy weight, avoiding excessive heat exposure, managing stress, and eating a balanced diet rich in antioxidants (vitamins C and E, zinc, selenium, folate) have all been shown to improve semen quality. However, due to the ~3-month spermatogenesis cycle, improvements take at least 2–3 months to appear in test results.
What is sperm DNA fragmentation?
Sperm DNA fragmentation testing assesses the integrity of the genetic material within sperm. High DNA fragmentation (>30%) is associated with reduced natural conception rates, lower IVF success, and higher miscarriage rates. It is not part of a standard semen analysis but may be recommended when standard parameters are normal but infertility persists, or after recurrent pregnancy loss.