A semen analysis is a fundamental diagnostic tool used to evaluate male fertility potential. This laboratory test measures several characteristics of the semen and the sperm it contains, providing a detailed snapshot of reproductive health. The analysis determines the health and viability of sperm, offering quantifiable data points that guide specialists in assessing reproductive function. Interpreting the report correctly means understanding which physical and cellular parameters are measured and what the established reference values indicate.
Initial Report Parameters: Volume, pH, and Viscosity
The semen analysis begins with an assessment of the ejaculate’s macroscopic characteristics, focusing on the fluid components. The volume of the sample is one of the first measurements, with a lower reference limit set at \(1.5 \text{ milliliters (mL)}\). A volume below this limit, known as hypospermia, may signal a blockage in the ejaculatory ducts or an issue with accessory glands, such as the seminal vesicles or prostate.
The \(\text{pH}\) level reflects the balance of secretions from the various reproductive glands. Semen is normally slightly alkaline, with a lower reference limit of \(7.2\). A lower, more acidic \(\text{pH}\) can suggest a problem with the seminal vesicles, whose alkaline fluid contributes the largest percentage of the total ejaculate volume.
Viscosity and liquefaction are also measured. The semen sample is initially thick and gel-like upon collection, and enzymes from the prostate gland must cause it to thin out, or liquefy, typically within 30 minutes. If the sample fails to liquefy properly, indicated by high viscosity, the sperm may be physically trapped within the thick fluid, preventing them from moving freely.
Interpreting Sperm Concentration and Total Count
Sperm concentration measures the number of sperm cells present in each milliliter of semen. The World Health Organization (WHO) sets the lower reference limit for concentration at \(15 \text{ million sperm per milliliter}\).
A concentration falling below this threshold is clinically termed oligozoospermia. If the laboratory analysis reveals no sperm cells, the condition is called azoospermia. A low concentration indicates a potential issue with sperm production in the testes or an obstruction in the reproductive tract.
The total sperm count is calculated by multiplying the sperm concentration by the total volume of the collected sample. The lower reference limit for total sperm number is \(39 \text{ million sperm per ejaculate}\). This metric is a strong predictor of fertility potential because it accounts for both sperm density and fluid volume.
Assessing Sperm Quality: Motility and Morphology
The analysis assesses the quality of individual sperm cells, focusing on their ability to move and their physical structure. Motility refers to the movement of the sperm, which is categorized into different grades. Progressive Motility (\(\text{PR}\)) is the most functionally significant category, describing sperm that are moving actively and traveling in a straight line.
The report also notes Non-Progressive Motility (\(\text{NP}\)), which includes sperm moving but not making forward progress. Immotile (\(\text{IM}\)) sperm show no movement at all. The lower reference limit for progressive motility is \(32\%\), while the total motility (progressive plus non-progressive) lower limit is \(40\%\). Low progressive motility is known as asthenozoospermia and severely reduces the sperm’s ability to reach the egg.
Sperm morphology refers to the physical shape and structure of the sperm, evaluating the head, midpiece, and tail. This assessment uses strict criteria, such as the Kruger criteria, to define a normal-looking sperm cell. A sperm is considered normal only if it possesses a perfectly oval head, an intact midpiece, and a single, uncoiled tail.
Even in fertile men, a large majority of sperm may have abnormal shapes. The lower reference limit for normal morphology is \(4\%\) of the sperm having a perfect shape. A finding below this threshold is termed teratozoospermia. A sperm may have excellent motility but poor morphology, meaning its abnormal shape prevents it from penetrating the egg, illustrating that movement and structure are independent factors of sperm quality.
Understanding Deviations and Next Steps
When one or more parameters fall below the established lower reference limits, the findings are given specific clinical names, such as asthenozoospermia for low motility or teratozoospermia for poor morphology. A combination of issues, such as low count, low motility, and poor morphology, is commonly referred to as oligoasthenoteratozoospermia.
A single abnormal semen analysis result is rarely definitive for a diagnosis. Semen quality can fluctuate significantly due to factors like recent illness, stress, or the duration of abstinence prior to collection. Specialists almost always recommend a retest, typically two to three months after the initial sample, to confirm persistent low numbers or function.
If an abnormality is confirmed, the next step is to consult with a fertility specialist or a urologist focusing on male reproductive health. These experts interpret the combined results, looking for patterns and correlations between the different parameters. They discuss potential underlying causes, such as hormonal imbalances, genetic factors, infection, or lifestyle factors, and advise on management or treatment options.