The press have been reporting on a study from the journal Fertility and Sterility from last May which led the researchers to conclude that sildenafil citrate - better known as Viagra - ‘may adversely affect male fertility’. In other words, too many little blue pills could leave you firing blanks.

David Glenn, a consultant gynaecologist at Queen’s University Belfast took sperm samples from 57 men and mixed them in a Viagra solution - the equivalent to that found in the blood of a man who had taken a single 100-milligram tablet.

The drug made sperm more active than untreated sperm but also it damaged it in a way that means it would be highly unlikely to fertilise a female egg. Repeating the experiment on animls confirmed this - sperm from mice that had been given Viagra produced 40% fewer embryos than those on control pills.

‘There are two main concerns raised by these findings,’ Glenn told The Observer. ‘First, Viagra has become a widely used recreational drug. It is mixed with cocaine, for example, and is sold in clubs. Our work leaves open the possibility that there could be a cumulative effect from taking Viagra, however, which could pose serious fertility problems in later life.’

The second concern is that Viagra is regularly used by IVF clinics. Glenn said: ‘I think it is worrying that some IVF clinics are using Viagra in order to boost fertility results. Couples that go there for treatment are, by definition, already having problems getting pregnant. Giving male partners something that could make the problem worse is scarcely the right approach.’

Independent research by The Observer confirmed that several British IVF clinics did use Viagra to men. However, reported The Observer, ‘others, such as the clinic at University College Hospital in London, said they did not (use the drug) because it had been found that Viagra could damage sperm’.