Sperm morphology, which refers to the shape, size and structure of sperm cells, is a crucial element in understanding male fertility. This includes evaluating the head, midpiece and tail of the sperm to determine its ability to move effectively and fertilise an egg. Abnormalities such as misshapen heads or abnormal tails can affect fertility, but not all abnormalities necessarily result in infertility. This blog will explore sperm morphology, how it’s assessed, and its influence on male fertility.
Understanding Sperm Morphology
Normal sperm typically have an oval head, a slender midpiece and a long tail—all essential for optimal movement and fertilisation. Abnormal sperm, on the other hand, may have issues like an oversized or round head, a bent neck or a coiled tail. These abnormalities, collectively referred to as abnormal sperm morphology, may impact the sperm’s ability to reach and penetrate the egg.
However, it’s important to note that some abnormalities are common. A man can still have a normal sperm count and achieve fertilisation even if many sperm cells do not have perfect morphology.
How Sperm Morphology is Assessed
Sperm morphology is assessed as part of a semen analysis that evaluates sperm count, motility, and shape. During this test, a sample of semen is examined under a microscope to evaluate the shape of sperm cells according to guidelines established by organisations like the World Health Organization (WHO).
- The assessment measures the size, shape and structure of sperm to determine if they have the ideal form needed for effective movement and fertilisation.
- Morphology results are expressed as a percentage of sperm with normal shapes. For example, a value of 4% or more is considered within a healthy range according to WHO standards; a percentage below this may indicate abnormal morphology.
To get an accurate picture of sperm health, it’s crucial to conduct at least three semen analyses, as factors like stress, illness or environmental influences can affect individual results. An average of these results offers a more reliable diagnosis. Conducting all tests at the same laboratory is recommended to ensure consistency and avoid variability between different lab practices.
WHO 2021 Update: Revised Sperm Morphology Standards
In 2021, the WHO released the 6th edition of its Laboratory Manual for the Examination and Processing of Human Semen, sets the lower reference limit for normal sperm morphology at 4% based on strict criteria (often referred to as Kruger’s criteria).
While the edition does not alter the fundamental assessment or interpretation methods, it emphasizes a systematic approach to evaluating sperm morphology and includes photographs to aid in distinguishing between normal and abnormal forms. This update impacts clinical evaluations and treatment planning for men undergoing fertility assessments.
The Acrosome: Its Role in Sperm Morphology
The acrosome is a critical structure located at the tip of the sperm’s head. It contains enzymes necessary for penetrating the outer layers of the egg (oocyte), making fertilisation possible.
A well-formed acrosome is vital for successful fertilisation. Abnormalities in its size, shape or enzyme content can hinder the sperm’s ability to bind and penetrate the egg, directly impacting male fertility. Such issues can be detected during sperm morphology analysis, providing insight into potential fertility challenges.
The Link Between Sperm Morphology and Male Fertility
The shape and structure of sperm are vital for its function. To fertilise an egg, sperm must swim efficiently, penetrate the egg’s outer membrane, and deliver genetic material. Abnormal sperm shapes can interfere with these processes:
- Defects in the head or tail may impair the sperm’s ability to swim through the female reproductive tract.
- Variations like tapered heads or coiled tails may not provide the structural advantage needed for successful fertilisation.
- Pinhead sperm may have diminished capacity to penetrate the egg, hindering conception.
While a high percentage of abnormally shaped sperm can correlate with male infertility, it does not always result in infertility. Some men with a low percentage of normal sperm morphology can still conceive naturally or with the aid of fertility treatments.
Advanced Testing Beyond Morphology
Sperm morphology offers insights into the external structure of sperm, but it doesn’t provide a complete picture of the genetic material within. Advanced tests like Sperm DNA Fragmentation (SDF) and Reactive Oxygen Species (ROS) testing are often used to evaluate the DNA quality of sperm.
Factors such as smoking, alcohol use, and exposure to environmental toxins can increase DNA fragmentation. In addition, lifestyle choices like high testicular temperature from sedentary work can also impact DNA integrity. The Sperm Chromatin Structure Assay ( SCSA® ) test at Andrology Center Coimbatore, offers a more detailed evaluation of DNA integrity. We are the only laboratory in India authorised to carry out this crucial test
Overcoming Abnormal Sperm Morphology with Fertility Treatments
Even if sperm morphology is outside the ideal range, there are effective fertility treatments available. Techniques like Intracytoplasmic Sperm Injection (ICSI) can be used to improve the chances of conception. ICSI involves selecting a single, morphologically normal sperm from the sample and injecting it directly into the egg. This method has been successful in cases where sperm morphology or motility is less than optimal.
Despite the stricter WHO guidelines, assisted reproductive technologies like ICSI show that achieving a successful pregnancy is possible even with suboptimal sperm morphology, given the right medical support.
Conclusion
Sperm morphology is a key aspect of male fertility assessment, but it is just one factor among many. While the shape of sperm is important, additional aspects like sperm count, motility and genetic health also play a crucial role in fertility. Comprehensive semen analyses, along with advanced testing methods like the SCSA, help diagnose potential issues and offer pathways for effective treatment.
If you have concerns about male infertility or sperm quality, consulting a fertility specialist is advisable. Understanding your sperm morphology and overall sperm health can lead to informed decisions and effective treatments, improving the chances of conception and enhancing reproductive health.
At Andrology Center Coimbatore, we offer diagnostic tests including both manual and AI-assisted semen analysis, the DFI (DNA fragmentation index) as well as related blood and hormone tests, to provide a comprehensive evaluation of male fertility. By staying informed and taking proactive steps, men can manage their fertility and explore solutions that align with their health and lifestyle.
