Jeremy Laurance: Discovery raises spectre of making men discardable

Men have never ranked high in the treatment of infertility. Twenty years ago it was not uncommon for an infertile couple to spend years in which the woman endured extensive investigations before doctors thought to examine the man. Men have always been more sensitive about their fertility, confusing it with potency (the capacity to have sex), but there was also less that could be done for men.

Yesterday's advance shows how far science has come to the aid of men - but throws up a host of new ethical problems.

The discovery that sperm can be grown from embryonic stem cells raises the prospect- though still distant - of a cure for male infertility. But it also raises the spectre of a baby born without a father.

If it is possible to create sperm from a collection of embryonic stem cells grown in a laboratory, then men may be redundant - a species who have served their time and are now discardable. Using stem cells in this way, even were it technically possible, would be illegal in the UK. But as a treatment for male infertility, using stem cells taken from spermatagonial tissue in the infertile male, it offers exciting prospects.

Infertility in men appears to be increasing. Currently, 40 per cent of cases are in men, 40 per cent are in women and 20 per cent are joint problems. But there are signs that this balance may be changing.

Figures presented to the European Society for Human Reproduction and Embryology showed that demand for Intra-Cytoplasmic Sperm Injection (ICSI) typically used for men with low fertility was up from 43 per cent in 1997 to 52 per cent in 2002. Treatment cycles involving ICSI now outnumber those involving ordinary IVF.

Some specialists believe environmental changes are putting male fertility under greater threat. The growth of oestrogen-like chemicals polluting the environment and factors in the food chain that disrupt the endocrine system are thought to be responsible for falling sperm counts .

Not only are men producing fewer sperm but the ones they do produce swim less vigorously. Men, like women, are putting off having a family until they are older and in both sexes, fertility declines with age.

Yesterday's discovery offers no quick fix. There are many technical, ethical and safety issues and there is a long way to go before these techniques are likely to be used in humans.