What affects men’s fertility?

Much emphasis is placed on the woman during a couple’s fertility journey. However, while it may seem obvious, the woman is only one part of the equation. In Australia, it’s estimated that 40% of infertility can be attributed to men.1,2 Furthermore, according to the Australian Institute of Health and Welfare, 8% of males over the age of 40 have tried unsuccessfully to have children.2

What does normal fertility in men require?

Fertility in men firstly relies upon the normal production of sperm, a process which is under hormonal control. Sperm must be produced in an adequate amount and be of normal shape and structure. This is vital in ensuring a sufficient number of sperm are able to propel forward and survive in the female reproductive tract, in order to reach and fertilise the egg.

Fertility in men also depends on the normal transportation of sperm from its site of production in the testicles. Sperm must be able to pass through a series of open passages so that it can exit via the urethra (the channel in the penis) during ejaculation.

What are the causes of male infertility?

Any abnormality in the production or transportation of sperm can result in male infertility. The specific causes of male infertility fall into four broad categories:

1. Abnormal sperm production

For the majority of men with abnormalities in sperm number, shape or motility (the ability of the sperm to move), there is no identifiable cause. However, there are a number of congenital and acquired causes of abnormal sperm production that may be responsible.

If abnormal sperm production is congenital, it means the condition causing the abnormality has been present from birth. One of these conditions is Klinefelter syndrome – a genetic condition in which the male has 47 chromosomes (rather than 46). Men with Klinefelter syndrome have small testes and do not produce sperm.

Another congenital condition that can cause abnormal sperm production is cryptorchidism, or undescended testes. Normally, during early development, the testes form in the abdomen and then descend into the scrotum (the sac that contains the testes). If this process does not occur, the testes remain situated in the abdomen – hence the term ‘undescended’. Men with undescended testes usually have lower sperm counts and poorer-quality sperm.

Abnormal sperm production can also be acquired, meaning that it results from events that occur in later life. Infection of the testes, most commonly by the mumps virus, is one acquired cause of sperm production abnormalities. Similarly, some drugs, including chemotherapy agents, can impair normal sperm production.

A condition called varicocoele involves enlargement of the veins of the scrotum. This can lead to scrotal pain, reduced testicle size and in some cases infertility; in other cases, men with varicocoele have normal fertility. In another condition called testicular torsion (twisting of the testis), a lack of blood supply can result in death of the testis, causing permanent loss of sperm production. This condition most commonly occurs in babies or young adolescents.

Finally, any trauma to the testes may also impair sperm production.

2. Sperm transport disorders

Structural abnormalities of the passages that transport sperm (i.e. epididymis, vas deferens, urethra) can cause infertility. As with abnormal sperm production, these abnormalities can be congenital or acquired.

In the vas deferens, blockage can be caused by previous sexually transmitted infections. It may also be the result of a vasectomy, which is a surgical procedure that intentionally cuts and ties the vas deferens as a method of permanent contraception. Although a vasectomy can be reversed surgically, there is no guarantee that fertility will return.

Lastly, difficulties with sexual intercourse can also prevent the passage of sperm into the female reproductive tract. These include erectile dysfunction (impotence) and premature ejaculation.

3. Hormone disorders

Because the production of sperm is driven by hormones, hormonal abnormalities can affect fertility. The main hormones that influence male fertility are gonadotropin releasing hormone (GnRH), LH (lueteinising hormone) and testosterone; abnormalities in these hormones may occur for various reasons. Additionally, imbalances in other hormones not directly involved in the male reproductive system can also affect male fertility.

4. Unknown (idiopathic) male infertility

Some men have consistently normal sperm (as determined by semen analyses), yet still fail to conceive with an apparently fertile female partner. Despite assessment and investigation, no underlying cause is found.

This list does not include all the possible causes of male infertility– however, it gives you a good indication of what a fertility specialist will be looking for in their assessment.

What lifestyle factors affect men’s fertility?

A person’s lifestyle seemingly has an impact on all facets of health – and this includes fertility. Lifestyle factors that may affect men’s fertility include:

  • Diet: Studies have demonstrated that men with healthy dietary habits tend to have better results on semen analyses. Low sugar and carbohydrate eating plans are best.
  • Exercise: Overall, men who are sedentary produce less sperm. They are also more likely to suffer from erectile dysfunction. However, balance is important – too much exercise can also have a negative impact on men’s fertility. Aim to exercise 3 to 4 times per week for 45 minutes.
  • Weight: Men with an abnormally high BMI (body mass index) – i.e. those who are overweight – are less likely to conceive. However, this is also true of men with abnormally low BMIs. Therefore, being in a healthy weight range is important in ensuring optimum fertility.
  • Smoking: Lower sperm quality has been observed in men who smoke. This effect is reversed within a year of quitting.
  • Alcohol: In men, heavy alcohol use can lead to sperm production abnormalities, erectile dysfunction and testosterone abnormalities. Therefore, men who are trying to conceive should reduce their alcohol intake.

Men’s fertility decreases with increasing age

You are probably aware that women become less fertile as they get older, but you may not know that men also experience a decline in their fertility (albeit to a much lesser degree). While it’s true that men continue to produce sperm through the entirety of their life, the quality of their sperm diminishes with age.

What tests are performed to assess male infertility?

The initial test for male infertility is a semen analysis. This assesses the volume of semen (the fluid that contains the sperm), sperm count and concentration, sperm motility and sperm shape. It may also test for the presence of sperm antibodies, which can impair functioning of the sperm. Some sperm analyses also assess the DNA in the sperm. It is important to have your sperm tested at an experienced laboratory.

If the sperm analysis is abnormal, the test may be repeated to confirm the result. If the sperm count is still abnormal in the repeat test, further investigation may be necessary to determine the cause. Usually this involves a series of blood tests and sometimes an ultrasound scan.

Concerned about your fertility?

If you and your partner have been struggling to conceive, it’s better to seek help early. As a fertility specialist, I am experienced in investigating causes of infertility (due to both male and female factors) and can work with you to determine your next steps. Contact my rooms to make an appointment by calling (03) 9418 8299 or booking online.


  1. McLachlam RI, de Kretser DM. Male infertility: the case for continued research. Med J Aust 2001;174:116–117.  ↩
  2. Collins HP, Kalisch D. The health of Australia’s males. Australian Institute of Health and Welfare 2011.  ↩

The information on this page is general in nature. All medical and surgical procedures have potential benefits and risks. Consult a healthcare professional for medical advice specific to you.


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