Health: Health check - Single sperm count

THE PUBLIC has no love for genetics. Manipulating the building blocks of life should, in the view of many, be off limits for scientists. There may be benefits from genetically modified food, even from cloning, but too much is at stake, ethically and in safety terms, to allow boffins free rein.

Strange, then, that the biggest genetic experiment of all - involving the birth of over 3,000 babies in the UK alone so far - is going on under our noses with barely a murmur of comment, let alone protest.

I am referring to ICSI - the injection of genetic material (in the form of a single sperm) into an egg to create an embryo. Its full title is Intra Cytoplasmic Sperm Injection and it is the fastest-growing method of in vitro fertilisation, according to the annual report of the Human Fertilisation and Embryology Authority, published last week.

The race that all sperm are involved in from the moment they are deposited in the vagina to reach the egg may have a purpose - to weed out damaged sperm which could pass their defects to the next generation. The act of sexual intercourse ensures a process of natural selection - a process over-ridden by ICSI.

What are the long-term consequences of tampering with nature in this way? No one knows. Some studies have suggested a slightly higher risk of congenital defects among ICSI babies, but others have shown no such increase.

One fear is that male children born by the method will inherit the infertility suffered by their fathers. Is a man's life ruined by the discovery that he cannot have children or is it an acceptable price for being born? Does he simply choose ICSI in his turn?

The HFEA has long been concerned by ICSI, but warnings of potential genetic consequences have zero impact. The desperate desire for a child guarantees they will be ignored.

The use of ICSI is almost certain to grow because success rates are now 40 per cent higher than with ordinary IVF. We have to face the fact that we are in the midst of the biggest genetic experiment in human history - and we will not know the outcome for another 50 years.