The biological clock ticks for men too, researchers find, with odds of parenthood falling with age

For men who are reluctant to start a family, it is an age-old defence: there is no need to rush into fatherhood.

And a host of celebrity dads seem to help prove the point, from 56-year-old George Clooney, a recent new father to twins; to rock star Mick Jagger, who became a father again in December at the ripe old age of 73; to opera singer Luciano Pavarotti, whose daughter Alice was born when her father was 68.

But men, just like women, can wait too long, doctors warn. A new study reveals that a couple’s chances of having a baby fall with the man’s age, to the point that it can have a substantial impact on their ability to start a family.

Laura Dodge, who led the research at the Beth Israel Deaconess Medical Centre and Harvard Medical School in Boston, said that couples should bear the findings in mind when planning a family. “When making this decision, they should also be considering the man’s age,” she said.

Scientists have long known that a woman’s chances of conceiving naturally drop sharply from the age of 35, but fertility research has focused so much on women that male factors are less well understood. “The impact of age seems to focus almost exclusively on the female partner’s biological clock,” Dodge said.

To investigate the impact of a man’s age on a couple’s chances of having a baby, Dodge and her colleagues studied records of nearly 19,000 IVF treatment cycles in the Boston area between 2000 and 2014. The women were divided into four age bands: those under 30, 30-35 year-olds, 35-40 year-olds, and those aged 40-42. The men were divided into the same age brackets with an extra band for the over 42s. Some of the couples had received up to six cycles of IVF.