Teratozoospermia refers to abnormal sperm morphology. Sperm morphology refers to the size and shape of the sperm. Any deviation from the normal size and shape of the sperms is referred to as teratozoospermia. A normal appearing sperm has an oval elongated head with the dark staining nucleus (DNA) and 1 or 2 empty spaces (vacuoles). The head is connected to the tail by a mid-piece which has a neck. Under the microscope at least 4-5% of sperms should appear normal. To be more specific teratozoospermia is diagnosed when more than 95% of sperms in a man’s semen sample is of abnormal morphology. However, this is highly subjective as it depends on the person looking under the microscope. Toxins, infections and Varicoceles again contribute to abnormal sperm morphology.
What does a normal sperm look like?
Let us read further to understand what a normal sperm looks like. The different parts of a sperm are head, neck, mid-piece and tail. A normal sperm is about 3-5 micrometer in length and 2-3 micrometer in width. The head is oval in shape and covered by a structure called the acrosome. The acrosome should be about 40-70% of the sperm size.
Sperm head defects:
- Large Head
- Small Head
- An Elongated Head
- Irregularly shaped head
- Globozoospermia or round headed sperm with absent acrosome.
The acrosome covering the head of the sperm may sometimes be too small or absent altogether. The head of the sperm may sometimes be totally detached from the rest of the sperm.
Neck and mid-piece defects of sperm:
The defects in the mid-piece and neck of the sperm may be in the form of:
- Asymmetric neck or mid-piece
- Bent neck
- Too thin or too thick neck or mid-piece
- Irregular neck or mid-piece
- Presence of abnormal droplet within the mid-piece
Sperm tail defects
The tail of the sperm may sometimes be:
- Bent in hairpin fashion
- With an abnormal terminal droplet
After a detailed description about normal and abnormal sperm morphology, if you are left wondering ‘does sperm shape affect fertility?’, you may want to read on to find out how actually it does affect male fertility.
Causes of Teratozoospermia:
Many a times the cause of teratozoospermia is unknown. Alterations in the sperm morphology ensue during the last stage of spermatogenesis. Some possible causes of teratozoospermia are:
- Cancer chemotherapy and radiotherapy. For the same reason men who are to undergo cancer treatment are advised to freeze their semen sample if they wish to become a father after recovering from the illness .
- Radiation exposure
- Some drugs that interact with sex hormones
- Diabetes mellitus and certain other chronic medical conditions
- Trauma to the testes
- Alcohol and drug abuse
- High fever and viral infections
- Acute stress
- Testicular infections
- Meningitis which is the infection of the covering layers of the brain
- Cancers such as Hodgkins lymphoma
- Autoimmune conditions such as Coeliac disease and Crohns disease
- Varicocele in which there is abnormal dilatation of veins of the scrotum hampering testicular blood flow
If none of the above causes are responsible for teratozoospermia, it may be a genetic problem and is the most serious scenario. If you are eager to find out how to test for teratozoospermia, we have the answers for you .
Sperm morphology test / Testing for Teratozoospermia
The semen sample collected is examined under a microscope after staining with a special papanicolau stain. More than 60% of sperms should be normal and less than 2-3 % should be immature. The sperms are examined carefully to look for the number of defects in each sperm. It may happen that a sperm has defects in only one part or that it has multiple defects. An index referred to as teratozoospermia index is employed to detect the most frequent type of defect in a semen sample.
The teratozoospermia index may range from 1 to 3. A teratozoospermia index around 1 indicates defect in one part is most frequently occurring, index around 2 means defect in two parts and an index of 3 means defect in three parts. The index is thus helpful in detecting the severity of sperm morphology defects.
Assisted reproductive techniques have made it possible for teratozoospermic men to have their biological offspring. As it is has already been mentioned, the chances of a teratozoospermic man naturally impregnating a woman are highly unlikely.
Assisted reproductive techniques are based on selecting the sperms with the best morphology for fertilization of an egg. The various techniques among which one is selected based on the needs of the couple are :
- Artificial insemination used in case of mild teratozoospermia .
- In-vitro fertilization is carried out by selecting best of the mans sperms, in case of moderate teratozoospermia .
- Intracytoplasmic sperm injection (ICSI) is used in severe cases of teratozoospermia or if all the above methods have failed. ICSI involves microinjection of the selected sperm into the ovum for fertilization so as to improve chances of fertilization .
- Intracytoplasmic morphologically selected sperm injection (IMSI) is a variation of ICSI with improved sperm recruitment by observing under high magnification light microscope .