Oligozoospermia and criptozoospermia
In this article we explain what oligozoospermia is, what types exist, how it is diagnosed, what the chances are of achieving a natural pregnancy and which treatment is most appropriate. We also look at cryptozoospermia, the most extreme form of this condition.
What is oligozoospermia?
Oligozoospermia, also known as oligospermia, is the presence of an abnormally low number of sperm in a semen sample.
According to the criteria of the 6th edition of the World Health Organization (WHO) manual (2021), the normal sperm concentration in a semen sample should be equal to or greater than 16 million per millilitre. If the sperm count is below this figure, it is called oligozoospermia and fertility problems may be present. It is advisable to assess more than one sample to confirm the diagnosis.
How is oligozoospermia detected?
The diagnostic method is a semen analysis (spermiogram), which, among other parameters, determines the number of sperm per millilitre of semen.
Mild, moderate and severe oligozoospermia
Oligozoospermia is classified into several types depending on sperm concentration:
- Mild: between 5 and 14 million sperm per millilitre of semen
- Moderate: between 1 and 5 million sperm per millilitre of semen
- Severe: fewer than 1 million sperm per millilitre of semen
What is cryptozoospermia?
A special case of oligozoospermia is cryptozoospermia. This is the term used when the number of sperm is below 100,000 per millilitre of semen.
Because there are so few sperm, they can sometimes only be found after centrifuging the sample and examining the sediment in detail, so it is essential that the analysis is carried out by a laboratory specialising in andrology. Its causes and treatment are similar to those of severe oligozoospermia.
Causes of oligozoospermia
The causes of oligozoospermia can be very varied:
- Partial obstruction of the ducts that carry sperm from the testicles to the urethra
- Abnormalities of the testicular veins (varicocele)
- Disorders of the epididymis
- Hormonal disorders
- Trauma or inflammation of the testicles
- Changes in semen caused by certain medicines, alcohol, tobacco or drugs
- Habits that raise testicular temperature (saunas, tight clothing, etc.)
Oligozoospermia and natural pregnancy
Oligozoospermia does not always prevent a natural pregnancy. In mild cases, especially if sperm motility and morphology are normal and there are no other infertility factors in the couple, a spontaneous pregnancy is possible, although it may take longer than usual.
As sperm concentration decreases, the chances fall. In severe oligozoospermia and in cryptozoospermia, a natural pregnancy is unlikely, so it is advisable to see a specialist and consider assisted reproduction techniques.
Treatment of oligozoospermia and cryptozoospermia
Patients with severe oligozoospermia can sometimes progress to cryptozoospermia and later to azoospermia (absence of sperm in the semen). For this reason, following this diagnosis it is important to take preventive measures such as sperm freezing to preserve the gametes.
In patients with oligozoospermia and cryptozoospermia, the most suitable treatment is in vitro fertilisation using ICSI (intracytoplasmic sperm injection), as the low sperm concentration can prevent the egg from being fertilised correctly by natural means.
When a treatable cause is identified, such as a varicocele or certain hormonal disorders, treating it can in some cases improve sperm concentration. In cryptozoospermia, if the number of sperm in the ejaculate is not sufficient for ICSI, it may be necessary to combine several samples or to retrieve sperm directly from the testicle.
Finally, it is important to note that there are measures such as taking antioxidants and following a healthy lifestyle that can improve semen quality, offering a more favourable prognosis for patients with mild oligozoospermia.