A sperm's journey to the egg can be perilous
Fertility problems receive a lot of attention - or at least women's do.
In this week's Scrubbing Up health column, Dr Allan Pacey argues male fertility problems are neglected, and there isn't enough research into how men can be helped.
Around one in six couples experience fertility problems at some point in their lives and seek advice from a doctor.
Tests show that between 30% to 50% of problems are with the male partner.
During any one year, millions of men throughout the world struggle to father children, and many more may not be aware of a fertility problem because they have not yet decided to start a family. Others may realise there is a problem and simply give up trying.
Of the many reasons why a man may not be able to father a child the most common is that he simply does not produce enough sperm, or that the sperm he does ejaculate are of poor quality.
In some European countries, such as Denmark, it has been estimated that up to 25% of young men have poor semen quality.
A worry is whether this proportion has increased in recent years, and whether today's men are as fertile as their fathers were.
Faced with a diagnosis that their sperm quality is poor, there is sadly very little that men can do to reverse the situation.
Unlike women, where fertility drugs can often be prescribed to stimulate the production of eggs, there are only very rare cases where the testicles can be simulated to produce more sperm.
Faced with a male partner with poor sperm production, the difficult decision facing many couples and their doctor is what assisted conception technique to opt for.
Prior to the early 1990s, there were just two main treatments to choose from.
The first was to place sperm directly into the woman's womb at the time of ovulation; a procedure known as intra-uterine insemination.
The second was to perform a cycle of in vitro fertilisation (IVF).
Each was intended to give the sperm a 'helping hand' to reach and fertilise an egg.
However, in both cases, several million good quality sperm were still needed from the man, and where this number could not be obtained, success rates were very low.
In such cases, the only real alternative was to use donor sperm, which raised difficult ethical questions for many couples.
But in 1992, the development of intra-cytoplasmic sperm injection (ICSI), where a single sperm is injected into an egg, gave comparable levels of fertilisation and embryo development to conventional IVF.
At a stroke, the medical management of male infertility was revolutionised, and ICSI became the single most important development in assisted reproduction techniques since the arrival of IVF itself.
There are now almost as many cycles of ICSI each year as there are traditional IVF, and as a consequence the need for donor sperm treatment has reduced markedly.
But whilst ICSI is obviously a success in terms of helping produce healthy babies for childless couples, it is easy to forget that it remains only a pragmatic solution to the problem of too few, or too poor sperm.
It is not a cure, and men who have fathered children through ICSI are still not fully fertile.
Moreover, in my opinion, the success of ICSI seems to have drawn our attention away from considering the biological causes of poor sperm production and attempting to find a cure.
As a scientist interested in this issue, I consider it vital to carry out the necessary basic research to understand the problem, but unfortunately all too often this area is not considered a high priority for funding alongside issues such as cancer research.
Surely the preferred choice for most sub-fertile couples would be to conceive their children naturally without medical intervention?
This would certainly be more fun, less stressful and cheaper given the fact that many couples have to pay for their own infertility treatment.
ICSI should be viewed not as the solution, but a temporary fix whilst we find an answer to the real problem.
Perhaps it may not be possible to find a cure for male fertility problems, and the biology will defeat us, but we won't know for sure unless we try.