Infertility is defined as the inability to conceive after 12 months of unprotected intercourse. Infertility affects 1 in 6 couples of childbearing age. In approximately 40% of infertility cases a female factor can be identified and in 40% a male factor. The remaining 20% of cases are due to combination of male and female disorders or remain unexplained. Semen analysis is an important step in the initial evaluation of an infertile couple. Semen analysis is also performed post vasectomy to determine if a patient has become sterile.
Semen analysis is performed according to WHO guidelines. Results are interpreted as follows:
- Volume of ejaculate is normally >2 mL.
- pH is normally 7.2 to 8.0. A more acidic pH suggests an abnormally high ratio of prostatic to seminal fluid.
- Normal sperm count is >20 million per mL. Counts between 10 and 20 million are considered borderline. Sperm count is performed in a Neubauer chamber.
- Both the percentage of motile sperm and the grade (speed) of motility on a scale of 0 to 4 are reported. Normal sperm have >50% motility and a grade of 3 or 4. A grade of 4 indicates rapid progressive movement. Sperm motility is as important as number.
- Sperm morphology is another important evaluation criterion. At least 200 spermatozoa are examined and the percentage of abnormal forms is reported. Spermatozoa are examined for defects involving the head, neck, acrosome and tail regions. A spermatozoan is generally considered normal if it has a smooth and oval head, an acrosome comprising 40-70% of the sperm head, symmetrical neck insertion into the head, a mid-piece with no large cytoplasmic droplets, and a uniform tail of regular width and length without coiling or bent configuration. More than 70% of spermatozoa should have normal mature morphology and at least 30% should have normal oval shapes. Abnormalities in head structure are associated with poor ovum penetration. Examples include double heads, giant and amorphous heads, pinheads, tapering heads and constricted heads. Spermatozoan tail defects may impede the migration of spermatozoa through cervical mucus.
- Germinal cell count should be < 4 million per mL. A higher number of germinal cells indicates a disorder in spermatogenesis because sperm usually mature within the epididymis prior to release. Germinal cells may be referred to as round cells in some reports.
- Spermatozoa viability is normally > 75%. Viability is assessed using a supravital stain.
- White blood cell count is normally < 1 million. Higher counts indicate genital tract infection.
If the patient will be involved in an assisted reproductive program, Kruger Strict Criteria are used to evaluate sperm morphology. Kruger criteria identify three threshold groups based on the percentage of normal spermatozoa: 0-4% normal forms, 5-14% normal forms, and greater than 14% normal forms. These groups are used as a predictive value in determining in vitro fertilization outcomes.
Post-vasectomy semen analysis is much simpler, consisting of only a sperm count. The first specimen should be collected two months after surgery and after a minimum of 10 ejaculations. Specimens are usually tested at monthly intervals until two consecutive monthly specimens show no spermatozoa.
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