Diabetic dads 'have smaller babies'

While there is no evidence that this is a direct result of the disease itself, it suggests that a common genetic factor is involved, they say.

They study, carried out by scientists at the Institute of Child Health in London and the University of Bristol, looked at the men born in the first week of March 1958.

Of the 11,276 41-year-old men and women contacted, 96 said they had type II diabetes - the kind that normally appears in adulthood.

Of these, 34 men and 24 women had had children.

The offspring of the fathers with diabetes on average weighed 186g (6oz) less than those from non-diabetic fathers.

There was no other obvious reason such as the height or weight, or social class of the father which might explain this.

In the mothers, there was no significant difference between diabetics and non-diabetics.

No direct link

There is no theory that suggests that the illness is a direct cause of reduced birthweight, particularly given the father's limited role in the pre-natal development of the foetus.

In addition, many of the men involved would have had these children at a time when they had no obvious sign of type II diabetes.

Instead, the researchers believe that the finding suggests that there is a genetic difference which contributes both to the chance of developing type II diabetes - and of being born slightly smaller.

A spokesman for Diabetes UK said that while the study only covered relatively few men and women, if the finding were true, it would have far more significance for the fathers of today.

She said: "Type II diabetes has become far more prevalent in recent years."