What does a semen analysis include?
The sperm analysis includes sperm concentration, number, motility, and morphology. For most men, they are most concerned about sperm motility and progression, but the morphology is also very important. At the beginning of the 20th century, researchers found that the morphological characteristics of human sperm are opposite to those of other mammals, with low homogeneity but high heterogeneity and high polymorphism, which means that the sperm head shape may be pyriform, tapered, round, amorphous, vacuolated and normal oval-shaped; the neck may be bent neck, asymmetrical insertion, too thick, and too thin; the tail may be bent, coiled, and too short in the specimen of the same person.
Therefore, some people may have a similar proportion of each sperm type, and some people may have more amorphous and vacuolated types. In addition, although there are differences in the morphology of sperms that were ejected each time, the morphology is a relatively stable variable compared to the number and motility.
What is the effect of sperm morphology on fertilization?
In the past, researchers have found that sperm morphology is related to Acrosome function. The acrosome is located at the top of the sperm head. When the sperm head touches the zona pellucida, the acrosome releases enzymes to dissolve the zona pellucida, and then the sperm fuses with the egg cell membrane to complete fertilization, so normal acrosome function is very important for natural fertilization.
Studies have pointed out that sperm with a small or round head shape will also have a lower proportion of the acrosome in the head (<30%), and the success rate of natural fertilization will also decrease. However, sperm with a Megalo head or long sperm head will also affect the fertilization rate and pregnancy rate, even if fertilization is performed by IntraCytoplasmic Sperm Injection (ICSI). The reason is that the cell nucleus shape of these sperm is often long, and their nucleus envelopes are prone to have abnormal structures, indicating that during meiosis of spermatocytes, errors are prone to occur when the homologous and sister chromosomes are separated, resulting in chromosomal abnormalities in sperm cells. In addition, researchers have also found that most of the zona pellucida, which with higher fertilization rate, are bound with normal sperm. This indicates that the sperm motility and shape are better, the easier to fertilize successfully.
How to interpret sperm morphology?
After the importance of sperm morphology was confirmed, the interpretation of morphology became more and more rigorous.
South African Dr. Kruger et al proposed the so-called Tygerberg Strict criteria, sperm morphology is analyzed under the most stringent conditions, and the ratio of perfect sperm is judged by a high-power microscope after staining. Currently, under the 5th edition of World Health Organization (WHO) in 2010, the parameters of normal spermatozoa are as follows:
| parameter | normal value | |
| head | shape | oval-shaped and smooth cell membrance |
| length | 4.1um | |
| width | 2.8um | |
| proportion of the acrosome in the head | 40-70% | |
| others | number of vacuole in acrosome ≦2 and propotion <20%; vacuole in non-acrosome part =0. | |
| midpiece | length | 4um |
| width | 0.6um | |
| others | Excess cytoplasm ≦1/3 head width | |
| tail | length | 45um |
In addition, Computer-Aided Sperm Analysis (CASA) has also been added to sperm morphology interpretation. The system will directly analyze the staining results objectively. In addition to the above parameters, it also includes parameters that are difficult to interpret, such as Perimeter, Head area, Ellipticity, Midpiece angle, etc. These parameters can provide a more comprehensive sperm morphology assessment for doctors to make a diagnosis. Stork fertility center is currently using this system.
The CASA computer-assisted sperm analysis system can accurately and quickly analyze the activity, quantity, and morphology.
What should I do if the sperm count is low and substandard?
In modern men, due to factors such as working under great stress, smoking, lack of exercise, and environmental pollution, in recent years, the normal sperm ratio, motility, and the number of sperm have been declining. This means that the number of normal sperm to successfully fertilize an egg is decreasing, which is one of the reasons why it is difficult to get pregnant naturally. If so, fertilization by ICSI and selection of sperm with good motility and shape with a high-resolution microscope (6000x magnification) can solve this problem.
