Next online forum (live on January 9, 1pm): maximising fertility for men and women. To ask Dr Thomas Stuttaford your question on this topic and to read other recent topics he has answered click here

I am married to a man 25 years older than myself who has grown-up children. As I am 34 and childless I am hoping to become pregnant soon. I’ve read that there is a greater risk of genetic disorders if the father is older. How great is this risk and should I try to get pregnant at all?

Older men, provided that they survive, often make excellent fathers. Although they may not be at their best knocking a football about they are likely to be less absentee than younger men and are not so driven or beholden to their professional masters. Well known older fathers have included Charlie Chaplin, Pablo Picasso, Michael Douglas and Augustus John.

With the increase in life expectancy, the number of divorces and remarriages and a tendency for women to marry slightly later, the reader’s question is being asked increasingly often. Unfortunately there is no conclusive answer.

The changes in the male testes related to ageing are well documented and it is known that these result in a decrease in testicular size and reduction in the amount of testosterone produced. However, it is impossible to correlate these changes with any alterations in the number, morphology or function of the sperm.

Modern science has demonstrated a 20 per cent increased risk in children of older fathers suffering from a handful of relatively uncommon congenital abnormalities. This certainly shouldn’t discourage the reader, but it is an indication that careful prenatal testing is necessary. Even so, the risk is enough for American fertility clinics to reject semen from donors over 50.

However, there is no conclusive evidence that the familial link affecting the incidence of early-onset Alzheimer’s, schizophrenia, prostate and some other cancers is any higher than in children of younger parents or, if higher, that it can be definitely related to age of the father rather than environmental factors.