In the investigation of male factor infertility, a semen analysis shows: volume 2 mL, sperm concentration 4 million/mL, total motility 30% (progressive motility 20%), normal forms 3% (strict Kruger criteria). According to WHO 2021 reference values, which specific parameter(s) are below the lower reference limits?

• A Concentration only is below limit; motility and morphology are within normal range
• B Concentration, total motility, and normal morphology are all below WHO 2021 reference limits ✓
• C Total motility and morphology are below limit; concentration is borderline but within the 5th percentile range
• D All parameters including volume are below WHO 2021 lower reference limits

Explanation

WHO 2021 5th edition reference values (updated from 2010): Volume ≥1.4 mL; Total sperm number ≥39 million/ejaculate; Concentration ≥16 million/mL; Total motility (progressive + non-progressive) ≥42%; Progressive motility ≥30%; Normal morphology (Kruger strict criteria) ≥4%. This patient: concentration 4 million/mL (below 16), total motility 30% (below 42%), normal forms 3% (below 4%). Volume 2 mL is above 1.4 mL, so volume is normal. Three parameters are below reference limits, constituting oligoasthenoteratozoospermia (OAT syndrome).

Reference: Shaw's Textbook of Gynaecology, 17th ed.

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