Sperm production starts at puberty. It takes about 72 days to make a sperm and the testicles continuously make sperm, unlike in women who are born with all the eggs they will ever produce.
Once sperm are made, they mature in the epididymis, the softer organ next to the testicles. Sperm travel along the vas deferens, a cord like tube running from the scrotum to the base of the penis where they combine with seminal fluid which is released during ejaculation.
Sperm production is sensitive to heat, and ideal conditions are a few degrees less than body temperature. This is the reason why testicles lie within the scrotum.
A sample needs to be produced by masturbation and analysed very soon after to produce a reliable result. So men are usually given an appointment for semen analysis to produce a sample at the clinic so it can be analysed within an hour. Despite many advances in medical technology, semen analysis is not done by a fancy machine but by a scientist assessing the sample down a microscope.
Three important factors are required for a normal semen analysis: the count, movement (motility) and appearance of the sperm (morphology).
A normal sample should have over 15 million sperm per millilitre of the sample. A third of sperm need to be moving forward, but only 4% of sperm need be normal in appearance for a sample to be considered normal. For example, many sperm are deformed, or in a state of decay.
Evidence suggests that on a population level, men’s sperm counts have been decreasing over the last 30 to 40 years. Possible explanations are changes in the environment, with more exposure to chemicals, and/or differences in the way sperm samples are analysed.
While sperm count has been decreasing, rates of testicular cancer are on the rise. So it is important for men to regularly self examine their testicles for lumps and bumps and consult their doctor if they have any concerns.
Approximately 1 in 8 couples will have difficulty conceiving. About a quarter of these will have a male factor problem. So it is essential for the male partner to undergo semen analysis as part of the initial investigation for fertility problems.
As sperm production is ongoing, sperm count is particularly susceptible to changes in health and lifestyle.
Male factor fertility problems fall into one of two categories: either a blockage or production type problem.
Blockages
Abscence of the vas deferens. This can be easily assessed by examination of the scrotum by a doctor.
Previous surgery can prevent sperm from reaching the ejaculate. Obviously, a vasectomy will do this, but hernia repairs, scrotal or testicular surgery may also affect sperm count. Prostate surgery can damage the valve which stops semen from going backwards into the bladder, so men who have undergone this surgery may be at risk of retrograde ejaculation.
Previous sexually transmitted infections (STIs) such as chlamydia or gonorrhoea can affect the testicles resulting in blockage of the vas deferens or impaired sperm production.
Production type problem
Varicoceles are varicose veins within the scrotum. This may increase the temperature within the testicle, impairing sperm production.
Several genetic problems are linked with low sperm count, or no sperm at all (azoospermia):
Kleinfelter’s syndrome is when a man is born with an extra X chromosome. This condition affects about 1 in 600 men and is associated with small testicles.
Cystic fibrosis or being a carrier for the condition can result in absence of the vas deferens.
Boys born with undescended testicles may have a genetic component. However, even if the position of the testicles is surgically corrected, they are likely to have fertility problems in the future. Undescended testicles is also associated with other hormonal problems affecting testicular function.
Much uncertainty still exists regarding the genetic component of men with a low sperm count. Many men with a low sperm count are likely to have a genetic component, but these genes are yet to be identified.
Testicular cancer can obviously affect sperm count, but men who have had a testicle removed, or born with one testicle, may have lower sperm count but often father children naturally with no problems.
Previous cancer treatment with chemotherapy can affect sperm production. Men with treatable cancers may be offered sperm freezing before starting chemotherapy.
Male factor fertility problems are treated depending on the problem identified. For example, erectile dysfunction can be treated with Viagra. Risk factors can be modified to improve sperm count, and a low or borderline sample must always be repeated after at least 3 months to see if the problem was temporary.
Supplements
Sperm production relies on many processes and there is an array of multivitamin products on the market to improve male fertility. However, there is no convincing evidence to demonstrate a significant benefit from this type of supplementation.
Sperm can be damaged by oxygen free radicals, and there is some evidence that anti-oxidants may improve fertility. However, a recent review recommended further research.
Intracytoplasmic sperm injection (ICSI)
ICSI is a type of IVF where a sperm is injected into each egg in the lab. Similar fertilisation rates are seen with ICSI compared with IVF (where sperm and eggs are mixed together) where there is no sperm problem.
Surgical sperm retrieval
When there are no sperm in the ejaculate, sperm can sometimes be recovered by an operation. For blockage type problems, sperm can be aspirated by a needle from the epididymis (Percutaneous Epididymal Sperm Aspiration (PESA)). In men with a production type problem, a specialist surgeon can open up the testicle and look for where sperm are likely to be made using an operating microscope (Microsurgical Testicular Sperm Extraction (Micro-TESE)). If sperm are recovered, they can be used for ICSI.
Donor sperm
When sperm cannot be retrieved, couples may decide to use donor sperm.