Sperm Morphology – Tests And Results
The morphology of sperm refers to the shape, size and appearance of sperms. It is imperative to mention that sperm morphology is one of the key determinants of male fertility.
What Is The Sperm Morphology?
Sperm cells are not all identical or look exactly the same, but minor differences in morphology doesn’t mean that sperm cells are abnormal or dysfunctional. Abnormalities in sperms may involve tail, mid-piece and/or head and consequently lead to abnormalities in sperm motility, movement, ascent in vaginal tract, ability to penetrate within the egg membrane or other vital functions.
Healthcare providers evaluate sperm morphology and other characteristics as part of the fertility analysis through semen examination. Mild abnormalities of semen alone are not always suggestive of infertility.
What Should You Know About Sperm Morphological Analysis?
Sperm morphological analysis involves assessment of semen sample under a microscope for structural or functional abnormalities. Following are the characteristics of a normal sperm:
- Rounded or oval, well-formed, smooth surfaced head. The length of sperm head should be under 5 to 6 μm; and width between 2.5 to 3.5 (μm)
- About 40 to 70% of the sperm should comprises of acrosome (enzymatic membrane that gives the ability to sperms to penetrate the egg
- Absence of large fluid filled organelles – ideally, there should be no more than 2 vacuoles, occupying no more than 20% of the sperm head
- The segment between tail and sperm head should be about the size of head but much slimmer
- Absence of abnormalities on the tail or head region
In the lab, semen analysis involves putting a small quantity of semen on the test tube; air drying it and adding a dye to make individual sperms more visual under the microscope. Other advanced techniques are also available besides traditional semen analysis under the microscope, such as computer-aided sperm morphometric assessment (CASA). Various research studies suggest that accuracy and sensitivity of computerized tests is much higherdue to minimal risk of human errors. Other advanced tests that can determine the quality of semen are:
- Comet assay
- DNA fragmentation test
- Tunnel assay
- (SCSA) or Sperm chromatin structure assay
What Are Some Factors That Can Alter The Results Of Microscopic Semen Analysis?
Ideally multiple semen analysis tests should be performed before reaching to a final assessment; this is because, several factors can interfere with the quality of results, such as:
- Mislabeling of the sample
- Human error
- Contamination of the semen sample
- Time elapsed between sample collection and processing
Semen Analysis Results Based On Sperm Morphology
Following are certain terms that are used by experts to describe sperm morphology:
- Teratozoospermia: A semen sample that contains a larger percentage of abnormal sperms is referred to as teratozoospermia.
- Normal sperm sample should have a score between 4 to 14% of the morphologically normal sperms. Pregnancy is usually difficult with a sample of less than 4% morphologically normal sperms.
If you have a higher percentage of morphologically abnormal sperms; you should speak to your healthcare professional to ascertain the cause. Pregnancy is usually possible with treatment or assisted reproductive techniques.
Besides morphology; other factors that determine the quality of sperms are:
- Percentage of alive sperms in the semen sample (also referred to as vitality of sperms)
- Fluidity of semen
- Movement or motility of sperms
- Measure of how quickly semen can liquefy
- pH of semen
- Appearance and viscosity of semen
- Serum levels of vital reproductive hormones like testosterone, estradiol, prolactin, sex hormone binding globulin and others
References
- van den Hoven, L., Hendriks, J. C., Verbeet, J. G., Westphal, J. R., & Wetzels, A. M. (2015). Status of sperm morphology assessment: an evaluation of methodology and clinical value. Fertility and sterility, 103(1), 53-58.