Teratozoospermia Overview

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Updated: 19-Sept-2022


Teratozoospermia, also called teratospermia, means low sperm morphology. Specifically when less than 4% of sperm in a semen sample is identified as morphologically normal.

This means more than 96% of sperm in males diagnosed with teratozoospermia has abnormal morphology (defects in the head, middle piece of tail of the sperm cell). These defects hinder the sperm from fertilizing the eggs and is one of the main causes of male infertility.

Teratozoospermia can be categorised into 2 types:

  • Polymorphic
  • Monomorphic

Polymorphic teratozoospermia is when the majority of the ejaculate contains spermatozoa with more than 1 type of abnormality. On the other hand, when most sperm cells display only one unique abnormality, this is called monomorphic teratozoospermia.

Examples of monomorphic teratozoospermia are globozoospermia and macrocephalic sperm head syndrome, also called macrozoospermia. However both these conditions are very rare and believed to affect less than 1% of infertile men.

Globozoospermia is characterised by round-headed spermatozoa with an absent acrosome, an aberrant nuclear membrane and midpiece defects.

Macrocephalic sperm head syndrome is defined as the presence of a very high percentage of spermatozoa with enlarged heads and multiple flagella.

Overall teratozoospermia is a serious condition which affects a males ability to conceive naturally. In fact, on average, only 1 in 20 males with teratozoospermia will get their partner pregnant within 12 months, according to the WHO reference values for human semen.

By the same reference, high numbers of sperm with abnormal morphology is actually quite normal among the male population.

Specifically, 1 in 4 males produce semen samples with at least 90% or more sperm displaying abnormal morphology.

However, the majority of these males will manage to successfully get their partner pregnant within 12 months.

These statistics highlight the limitations ‘normal sperm morphology’ has on the likelihood of pregnancy among couples trying to conceive naturally.

For males diagnosed with teratozoospermia, this usually means there is likely to be other factors hindering ones fertility.

Symptoms of Teratozoospermia

The symptoms of low sperm morphology are similar to men diagnosed with oligospermia or asthenospermia. The primary symptom is the inability to conceive a child despite 1 year of frequent and unprotected intercourse.

Other related symptoms may include:

  • Erectile dysfunction or low sex drive
  • Pelvic or urinary pain
  • Changes in body hair indicating hormonal abnormality

Diagnosis of Teratozoospermia

Infertility in a couple is defined as the inability to conceive despite 1 year of frequent and unprotected intercourse. At this stage, it is advised that both partners consult a Doctor since the inability to conceive frequently occurs due to a combination of issues arising from both male and female partners.

For males, the European Academy of Andrology recommends the following tests to be performed initially:

  • General physical examination to assess any sign of hypogonadism
  • Physical examination of the scrotum to assess; the volume and consistency of the testicles and epididymis, the total or partial absence of deferent ducts, the presence of varicoceles
  • Two semen analyses (3 months apart) according to the WHO guidelines

Semen samples can be collected in the clinic or at home following 2 to 7 days of sexual abstinence.

However, if collected at home, the sample should be kept at room temperature and delivered to the laboratory immediately.

The following table outlines the lower reference limits published by the WHO for semen analyses. Any value below these lower limits is considered abnormal.
Source: Cooper T G, et al. (2009)

Sperm parameterLower limit95% Confidence Interval
Volume1.5mL1.4 – 1.7 mL
Sperm concentration15 million/mL12 – 16 million/mL
Total sperm number39 million33 – 46 million
Morphology (Tygerberg method)4% normal form3 – 4% normal form
Vitality58% live55 – 63%
Progressive motility32%31 – 34%
Total (progressive and non-progressive) motility40%38 – 42%

Teratozoospermia is diagnosed when there is less than 4% morphologically normal sperm, and all other parameters are normal.

Laboratory Assessment

During assessment, the 3 main parts of human sperm (head, neck, tail) are carefully observed under a microscope with the help of hematoxylin and eosin staining.

A normal head should be:

  • Smooth and oval
  • 5-6 microns in length
  • 2.5 to 3.5 microns in width
  • 40-70% of the head covered by the acrosome
  • No large vacuoles, and ≤ 2 small vacuoles, in the acrosomal region covering < 20% of the sperm head

A large or several vacuoles indicates significant DNA damage.
Source: Pastuszek E, et al. (2017)

Neck (middle piece)

The area between the head and the tail, which is slightly wider than the base of the tail and about the same length as the sperm head. It contains the mitochondria, which generates the ATP required for the sperm’s movement.

Tail (flagellum)

The tail is approximately 10 times the head length and is made up of the same structural molecules involved in spermatogenesis (during mitosis and meiosis). Therefore, an abnormal tail can occur from the incorrect distribution of chromosomes.

At least 200 sperm cells are evaluated during this assessment, to minimise any sampling errors, and a percentage of normal sperm cells calculated.

The sample is considered to be morphologically normal if at least 4% of sperm do not show any visual defects.

Source: World Health Organization, (2021)

Some laboratories or clinics may also report morphological assessment according to Kruger’s strict criteria classification. Kruger’s strict criteria only classifies sperm as normal if the shape of the sperm cell falls within strictly defined parameters. This means all borderline forms are marked as abnormal.

Severity% of Normal Sperm
Mild teratozoospermia10-14%
Moderate teratozoospermia5-9%
Severe teratozoospermia<5%
Kruger’s Strict Criteria Classification

Although, males with severe teratozoospermia, according to Kruger’s strict criteria, do not necessarily display impaired fertility, during either natural conception or ART cycles.
Source: Kovac J R, et al. (2017); Hotaling J M, et al. (2011)

Additional Tests

Based on initial results, your Doctor might recommend additional tests to determine or rule out potential causes of teratozoospermia.

These additional tests may include:

  • Scrotal ultrasound to look at the testicles and surrounding tissues
  • Blood tests:
    i) to determine the level of hormones secreted by the testicles and pituitary gland
    ii) or signs of genetic abnormality
  • Other less commonly used tests:
    i) Biopsy of the testicles to determine if there is normal production of sperm
    ii) Anti-sperm antibody tests to check if the immune system is attacking the sperm cells
    iii) Specialised sperm function test to determine the attaching potential of the sperm cells

Risks associated with Teratozoospermia

Men suffering from abnormal sperm parameters are susceptible to further issues such as:

  • Stress, loss of self-esteem and relationship issues due to difficulties trying to conceive.
  • Increased risk of cancer.


Several studies to date have found an association between abnormal semen analysis, including poor morphology, and a higher risk of cancer. Although the exact reason for this link has yet to be identified infertile men should consult their Doctor to discuss long-term monitoring strategies.

Causes of Teratozoospermia

Possible causes of teratozoospermia (0-4% normal sperm morphology) include genetic defects, hormonal imbalance, varicoceles, infection, obesity, smoking, drugs, alcohol, chemicals and heavy metals.

Fortunately, the majority of teratozoospermia cases is not caused by genetic defects. Only the rare monomorphic teratozoospermia condition is strictly linked to genetic defects.

This means for the majority of males, diagnosed with teratozoospermia, sperm quality should improve after intervention.


In a systematic review containing 19,967 males, normal consumption of caffeine has no significant effect on sperm morphology.

However, excess consumption of caffeine (4 or more cups of coffee per day) significantly increases the percentage of abnormal sperm morphology, and leads to decreased implantation rates in subfertile males undergoing ICSI treatment
Source: Karmon A E, et al. (2017); Ricci E, et al. (2017)

Treatment of Teratozoospermia

Treating teratozoospermia is a step-by-step process. The first step towards treatment is diagnosing and understanding the exact cause of teratozoospermia in your individual case.

Once a diagnosis has been made, your Doctor will recommend one (or a combination) of the following treatment options for teratozoospermia:

  • Expectant management
  • Lifestyle modification
  • Medication
  • Surgery
  • Supplements
  • Assisted Reproductive Technology


Questions or comments?