## Definition of Oligozoospermia **Key Point:** Oligozoospermia is defined as a sperm concentration of **less than 15 million spermatozoa per milliliter** of ejaculate, according to WHO 2021 guidelines. ## WHO 2021 Reference Values | Parameter | Lower Reference Limit | |-----------|----------------------| | Semen volume | ≥ 1.4 mL | | Total sperm count | ≥ 39 million per ejaculate | | Sperm concentration | ≥ 15 million/mL | | Total motility | ≥ 40% | | Progressive motility | ≥ 30% | | Vitality (live spermatozoa) | ≥ 54% | | Sperm morphology (normal forms) | ≥ 4% | **High-Yield:** The question specifies normal motility and morphology, which rules out asthenozoospermia (motility defect) and teratozoospermia (morphology defect). The isolated abnormality is therefore the **sperm count**. **Clinical Pearl:** Oligozoospermia may result from testicular dysfunction (primary hypogonadism), hormonal deficiency (secondary hypogonadism), or post-testicular obstruction. Further workup includes FSH, LH, testosterone, and imaging if indicated. **Mnemonic:** **OAT** = Oligozoospermia, Asthenozoospermia, Teratozoospermia — the three main semen abnormalities in male infertility.
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