What are the World Health Organization (WHO) parameters for a normal semen analysis in adult males of reproductive age?

WHO Parameters for Normal Semen Analysis

The World Health Organization establishes the following lower reference limits (fifth centiles) for normal semen analysis: volume ≥1.4 mL, sperm concentration ≥16 million/mL, total sperm number ≥39 million per ejaculate, progressive motility ≥30%, total motility ≥42%, vitality ≥54% live, and morphologically normal forms ≥4.0%. 1

Core Reference Values

These parameters are derived from analysis of 3,589 males from 12 countries across 5 continents who successfully fathered pregnancies within 12 months, representing the most comprehensive international dataset available 1. The specific reference limits with 95% confidence intervals are:

• Semen Volume: 1.4 mL (1.3-1.5 mL) 1
• Total Sperm Number: 39 million per ejaculate (35-40 million per ejaculate) 1
• Sperm Concentration: 16 million/mL (15-18 million/mL) 1
• Progressive Motility: 30% (29-31%) 1
• Total Motility: 42% (40-43%) 1
• Vitality: 54% live (50-56%) 1
• Morphologically Normal Forms: 4.0% (3.9-4.0%) 1
• pH: ≥7.0 1

Critical Collection Requirements for Accurate Results

Proper specimen collection is absolutely essential, as improper technique invalidates all results regardless of laboratory quality. 2 The following protocol must be followed:

• Abstinence period: 2-3 days before collection—inadequate abstinence significantly affects volume and concentration, invalidating results 3, 2
• Collection method: Masturbation or intercourse using specialized semen collection condoms 3
• Temperature maintenance: Keep specimen at room or body temperature during transport 3
• Analysis timing: Examine within 1 hour of collection for fertility evaluation (within 2 hours for post-vasectomy analysis) 3
• Sample preparation: Use fresh, well-mixed, uncentrifuged sample, as centrifugation interferes with motility assessment 3

Interpretation Framework: Multi-Parameter Assessment Required

Assessing a combination of several ejaculate parameters is a better predictor of fertility success than any single parameter, with discriminatory power comparable to diagnostic laboratory tools in other areas of modern clinical medicine. 1 Single-parameter assessments often show discriminatory power close to chance (ROC-AUC near 0.500) 1.

Number of Analyses Required

• Two semen analyses at least one month apart are required for initial male infertility evaluation due to significant intra-individual variability 1, 2
• A single ejaculate analysis is sufficient to determine the initial investigation pathway, but repeat testing is mandatory if abnormalities are found 1

Clinical Interpretation Patterns

Low Volume with Acidic pH

• Ejaculate volume <1.4 mL with pH <7.0 suggests ejaculatory duct obstruction or congenital bilateral absence of the vas deferens 1
• Males with normal semen pH (≥7.0) are unlikely to have complete distal genital tract obstruction 1

Severe Abnormalities Requiring Additional Testing

• Sperm concentration <10 million/mL: Order endocrine evaluation including serum testosterone and FSH 2
• Severe oligospermia (<5 million/mL) or azoospermia: Order genetic testing including karyotype and Y-chromosome microdeletion testing 2
• Ejaculate volume <1 mL: Order post-ejaculatory urinalysis to evaluate for retrograde ejaculation (except in bilateral vasal agenesis or hypogonadism) 2

Critical Pitfalls to Avoid

Laboratory Quality Control Issues

Poor adherence to WHO standardized methods is a major problem across andrology laboratories worldwide, making laboratory selection crucial. 3 Laboratories should demonstrate:

• Documented quality control procedures and ISO 15189 accreditation to WHO standards 3
• Well-trained staff capable of identifying and correcting errors 3
• Validation performed for each specific laboratory setting and sample type 3

Common Interpretation Errors

• Assuming normal semen analysis equals fertility: 25% of infertility cases remain unexplained despite normal conventional parameters 2
• Focusing on single parameters: This approach lacks sufficient predictive value and should be avoided 1
• Substantial overlap exists in semen parameters between fertile men and those in infertile couples, meaning results cannot definitively determine fertility status 3

Beyond Basic Parameters

Semen analysis is only part of the investigation of male fertility potential. 1 Complete evaluation must include:

• Medical history including frequency and timing of intercourse, duration of infertility, prior fertility, childhood illnesses, systemic illnesses, and sexually transmitted diseases 2
• Physical examination assessing penis, testicular size and consistency, vas deferens and epididymides presence and consistency, varicocele presence, body habitus, and secondary sex characteristics 2
• Lifestyle factors including testosterone/anabolic usage, cryptorchidism history, and scrotal infections 1