Women over the age of 35 who are planning to have a child are often well aware of their biological clock.

And a study suggests that the influence of paternal age could play a more vital role than previously thought – if they want to have IVF.

Analysis of nearly 19,000 IVF cycles revealed that for women under 35 or over 40, the age of their male partner doesn’t make a significant difference to their chances of conceiving.

But there was a “significant decrease” in the live birth rate for women between the ages of 35 and 40 if the partner was 40 or older.

The results can help shape fertility advice for couples trying to conceive. The researchers said they would challenge traditional assumptions that a partner’s age should always be a primary consideration.

Prof. Gita Nargond, medical director at Create Fertility, one of the study’s authors, told The Observer: “Obviously it is very important not to ignore paternal age when it comes to educating couples about fertility outcomes. It is clear that a woman’s age plays a large role. But not all of the focus has to be on her biological clock. We now know that for women in a certain age group, paternal age is more important than previously thought when it comes to live birth rates.”

The study was based on an analysis of anonymised data from the UK Fertility Regulatory Authority and the Human Fertilization and Embryology Authority.

It revealed that the live birth rate for women between 35 and 40 years decreased from 32.8% when the father was less than 35 to 27.9% when the father was between 40 and 44 years old. When the male partner is over 55 years old, the live birth rate was 25%.

Nargond, a consultant gynecologist at St George’s Hospital in Tooting, south London, said the study suggested the eggs of younger females had the ability to “repair the higher incidence of DNA damage in the sperm of older males”. She also said the potential ability of both the egg and sperm to “repair the effects of the aging process” needed to be better understood.