What Is Sperm Morphology? – Meaning & Normal Range

By BSc, MSc (embryologist), BSc (embryologist), MD, PhD (gynaecologist), BSc, MSc (embryologist) and (invitra staff).
Last Update: 05/25/2020

Sperm morphology is a parameter that is analyzed in the seminogram to see if there are abnormal spermatozoa in the semen, in what quantity they are found, and what alterations these cells have.

When a semen sample does not fulfill the minimum values of normal morphology, it is said that it shows teratozoospermia.

It is important to keep in mind that all men produce abnormal sperm and that a large portion of the sperm in a semen sample considered normal is abnormally shaped.

How do I know if my sperm is normal?

In order to study the morphology of male gametes, it is necessary to fix a small sample of the total ejaculate on a slide, which implies the death of the sperm. This prevents this sample from being used after its evaluation, but it will serve as a representation of the rest of the total seminal sample.

Once fixed, a biological stains, such as hematoxylin-eosin, is performed: eosin, binds to the electropositive elements of the cell, and has a pink coloring and hematoxylin binds to the electronegative molecules of the sperm, obtaining a bluish coloring.

The stain of the different structures allows a better observation under the microscope by increasing the definition of the membranes.

To assess the shape of a spermatozoon, its three main structures are observed: head, intermediate piece, and tail.

  • The head of the spermatozoon should be oval and smooth, 5 to 6 microns long and 2.5 to 3.5 microns wide. The acrosome should cover 40-70% of the head volume, and if there are vacuoles they should be scarce and occupy less than half of the head volume since if they are numerous or large it may mean that the DNA is damaged.
  • The middle piece or neck, as its name indicates, is located between the head and the flagellum, and it is a slightly wider area than the base of the tail. Its function is primordial because it houses the mitochondria, considered the motor of the sperm's movement, as they are responsible for generating energy.
  • The flagellum or tail is made up of the same structural molecules responsible for the correct distribution of chromosomes in mitosis and meiosis, so an irregular flagellum will reflect problems in the distribution of chromosomes, and above all, its movement will not be able to compete with the batting of a normal spermatozoon.

The evaluation of the sperm stained sample consists of counting the number of normal and abnormal sperm. Generally, 200 sperm are evaluated and then the percentage of normal-shaped sperm is estimated.

Abnormal spermatozoa: causes and alterations

Alterations in morphology can have a genetic origin, hence the importance of presenting a correct morphology. A spermatozoon whose genetic information, half of the future embryo, is not well coded and organized will not result in a viable embryo.

In addition, normally shaped sperm (in blue in the image below) swim faster and more adequately. In contrast, most abnormal spermatozoa are immotile or have a slow movement.

At the beginning of the sperm morphology study, there was a list of anomalies and if it did not comply with them, the spermatozoon was determined to be normal.

With the passage of time, it was seen that the variety of alterations was so great that it was decided to standardize the structure of a spermatozoon with good morphology, and deviations from this pattern are considered alterations (in pink in the image below).

Sperm with abnormal morphology may have an abnormal head, mid-piece and/or tail. Thus, there may be the following abnormalities:

  • Head alterations: spermatozoa without head (pinhead), small head, amorphous, round, elongated, large head (globozoospermia), pear-shaped (pyriform), with large acrosome, with small acrosome, without acrosome, with many vacuoles, with large vacuoles or with two heads.
  • Tail alterations: spermatozoa without tail, coiled tail, short tail, long tail, folded tail or double tail.
  • Alterations in the intermediate piece: spermatozoa without a middle piece, curved, asymmetrical, thickened, thin, irregular or with a bulge of more than one third of the head area.

There are very clear alterations, such as the duplication or absence of these structures, double-tailed, microcephalic or macrocephalic sperm, which can never give rise to a naturally viable embryo.

According to the WHO criteria, a value equal to or greater than 4% of spermatozoa with normal morphology is considered within the normal values. If the rate of abnormalities is greater than 96%, we are dealing with a case of teratozoospermia.

There is another criterion for analyzing the morphology that is somewhat stricter: Kruger's or morphology criterion, according to which the limit of normality is 14%, i.e. a sample with more than 86% of its abnormal spermatozoa will be considered teratozoospermia.

Is there treatment or not?

A man whose spermatozoa show a deteriorated morphology, i.e. he suffers from teratozoospermia, may find it more difficult to achieve pregnancy naturally, and even impossible in some cases.

Although teratozoospermia is not one of the most serious seminal problems, it will normally be necessary to resort to assisted reproduction in order to have children of one's own, especially in the most serious cases.

Depending on the degree of the condition and other factors that affect fertility in both men and women, the specialist will determine the most appropriate reproductive treatment, whether it is artificial insemination or in vitro fertilization.

This is what Dr. Jose Sánchez says:

The most suitable technique is undoubtedly ICSI or intracytoplasmic sperm injection, which consists of selecting the sperm with the best morphology and introducing them into the cytoplasm of the oocyte.

In milder cases, sperm morphology can be improved with an adequate diet, reducing caffeine consumption and avoiding tobacco and drugs.

There are also specific food supplements that prevent damage to the DNA produced by free radicals and contain vitamins and minerals necessary for proper sperm production and maturation.

These supplements must be taken for at least 3 months, which is the time it takes for sperm to be produced from scratch and mature.

FAQs from users

What are the causes of altered sperm morphology?

By Dr. María Arqué MD, PhD (gynaecologist).

Teratozoospermia is the alteration of sperm morphology, either by presenting defects in their head, intermediate piece, or tail.

According to the World Health Organization (WHO) criteria for 2010, a man has teratozoospermia when more than 96% of his spermatozoa have a strange or abnormal morphology.

There are several causes that provoke alterations in morphology and there are not always easy to diagnose, such as genetic alterations, chemotherapy, testicular disorders, unhealthy lifestyle habits, seminal infections, or pathologies like diabetes mellitus, meningitis, etc...

Some of these factors can cause reversible teratozoospermia, which disappears when the fever, infection, or periods of stress are reversed.
Read more

Can an abnormal sperm fertilize? Is pregnancy possible?

By Sara Salgado BSc, MSc (embryologist).

Yes, abnormal sperm is able to fertilize but most likely will not since those with normal shape move faster and will have it easier to reach the egg.

Depending on how the sperm are altered and how many abnormal sperm there are, the likelihood of pregnancy will be higher or lower.

For example, in spermatozoa without head (no genetic content) or with a small or absent acrosome (necessary to penetrate the egg) fertilization will not take place since they lack an essential part for the process.

Can abnormal sperm cause a miscarriage?

By Sara Salgado BSc, MSc (embryologist).

That might happen. The altered sperm may have genetic abnormalities that make it difficult or impossible for the embryo to form or develop, so it may not be viable and may stop growing, causing a miscarriage.

Depending on the gene or genes affected, embryonic development would stop at one point or another, depending on when they have to start expressing themselves; in other words, if the gene that is defective is very important in the first few weeks of pregnancy, an early abortion would occur because it does not contain adequate information for its development.

Can there be abnormal sperm from varicocele?

By Sara Salgado BSc, MSc (embryologist).

Varicocele is the cause of approximately 40% of male infertility cases. It produces a decrease in sperm production capacity, mainly due to an increase in testicular temperature and free radicals.

Therefore, it decreases both the concentration and the mobility of the spermatozoa and it seems that it is also related to the appearance of anomalies in the sperm morphology such as alterations in the head.

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Authors and contributors

 Cristina Mestre Ferrer
Cristina Mestre Ferrer
BSc, MSc
Bachelor's Degree in Biological Sciences, Genetics & Human Reproduction from the University of Valencia (UV). Master's Degree in Biotechnology of Human Assisted Reproduction from the UV and the Valencian Infertility Institute (IVI). Embryologist at IVI Barcelona. More information about Cristina Mestre Ferrer
 José Antonio Sánchez Férez
José Antonio Sánchez Férez
Bachelor's Degree in Biology from the University of Murcia. Vast experience as an embryologist, biologist, and researcher. Currently, he works as a Clinical Embryologist at Instituto Murciano de Fertilidad (IMFER). More information about José Antonio Sánchez Férez
Dr. María Arqué
Dr. María Arqué
Doctorate in Reproductive Medicine at the Autonomous University of Barcelona, specializing in Obstetrics and Gynecology. Dr. María Arqué has many years of experience as a Reproductive Medicine and Gynecologist Consultant and currently works as Medical Director at Fertty International. More information about Dr. María Arqué
Licence number: 080845753
 Sara Salgado
Sara Salgado
BSc, MSc
Degree in Biochemistry and Molecular Biology from the University of the Basque Country (UPV/EHU). Master's Degree in Human Assisted Reproduction from the Complutense University of Madrid (UCM). Certificate of University Expert in Genetic Diagnosis Techniques from the University of Valencia (UV). More information about Sara Salgado
Adapted into english by:
 Romina Packan
Romina Packan
inviTRA Staff
Editor and translator for the English and German edition of inviTRA. More information about Romina Packan

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