Definition - What does Sperm Morphology mean?
Sperm morphology refers to the size and shape of sperm. Sperm morphology is measured during a semen analysis, which is typically performed on men undergoing fertility testing. All men produce some degree of abnormal sperm, it is the ratio of abnormal to normal sperm that has the potential to impact fertility.
At least 4% of sperm should have normal morphology. This means that having at least 4% of sperm with a normal morphology is less likely to impact fertility.
FertilitySmarts explains Sperm Morphology
In addition to sperm morphology, a semen analysis also measures sperm count, concentration, motility and the volume of semen. The semen is analyzed under a microscope and the percentage of normal sperm is estimated. Strict (Kruger) criteria look at multiple sperm characteristics.
Features of a Normally Shaped Sperm
A typical sperm is shaped similar to tadpole:
- An oval-shaped head
- A defined cap on the top of the head (acrosome)
- Neck with no abnormalities
- Midpeice with no abnormalities
- Long tail with no abnormalities
While abnormalities can occur in any of these areas, the importance is that these defects can impact the ability of sperm to locate and fertilize an egg. Examples include a misshapen head or a split tail.
Abnormally Shaped Sperm Can Still Fertilize an Egg
Yet, abnormal sperm can still fertilize an egg. One study found that 22.9% of men with 0% normal morphology were able to conceive naturally, compared to 55.6% of the men with normal morphology. Additionally, these misshapen structures do not necessarily mean that there are problems with genetic material.
- Men with a complete absence of normal sperm morphology exhibit high rates of success without assisted reproduction. (2017).
- Sperm Morphology (Shape): Does It Affect Fertility?. (2014).