A Norwich Union Healthcare report says that two and a half million men in the UK could have fertility problems - this is about 9% of the male population.

Many doctors say that smoking could be a factor. This is a puzzling conclusion - thirty years ago over 50% of the male population smoked, now less than 25% smoke, but fertility problems during this period have increased. Some doctors say alcohol may also play a part in this increase (we do not have statistics for alcohol consumption in the UK over the last 30 years among adult males).

Some doctors say stress could be playing a part.

Doctors say that the number of sperms per ejaculation has gone down significantly over the last 30 years. The quality of the sperm has also deteriorated.

There is concern that an increase in infertility will accelerate an already ageing population.

When couples have difficulty in conceiving a child, male infertility accounts for just over 30% of cases.

The report also found that most men see infertility as a female problem. The majority are not aware that male infertility accounts for one third of difficulties in conceiving.

Many have written to us at Medical News Today in confusion:

1. If smoking has dropped, why has infertility increased. Surely, doctors are aware of smoking rates over the last 30 years. Why do they still blame smoking?

2. Men are much fatter than they used to be. Why was this not mentioned by doctors? Obesity and overweight must be a factor, surely?

3. Men lead a more sedentary life than they used to.

4. Could it not be something in the environment? There are many more cars than there used to be, more pollution, our diets are less ‘fresh' than they used to be (we eat more processed foods loaded with additives).