Among the one in seven couples now classed as infertile, the “male factor” has been found to be the most commonly identified cause. As many as one in five healthy young men between the ages of 18 and 25 produce abnormal sperm counts. Even the sperm they do produce is often of poor quality. In fact only between 5 and 15 per cent of their sperm is, on average, good enough to be classed as “normal” – and these are young, healthy men.