Why women who wait until their thirties ‘make better mothers’

They are more likely than younger counterparts to be financially secure and in stable relationships.

They are also happier to put their jobs on hold because they have already achieved many career goals.

Older mothers also tend to enjoy better health and live longer.

The findings, which appear in a book by Professor Elizabeth Gregory, will be welcomed by the growing numbers of women who are choosing to delay motherhood until well into their 30s.

The average age at which women in Britain are giving birth has slowly risen to 29 while there has been a much sharper increase in the numbers choosing to start families in their late 30s and early 40s.

More than 22,000 women over 40 had babies here last year, a quarter of them for the first time. And ten times as many women have their first child between 35 and 39 nowadays than in 1975, with 13 times as many between 40 and 44.

The trend is typified by high-profile mothers such as Jennifer Lopez, who is pregnant at 38, Halle Berry, who is expecting at 41 and Desperate Housewives actress Marcia Cross, who had twins at 44.

Professor Gregory, who is director of women's studies at the University of Houston in Texas, said: "I have found an overwhelming number and range of reasons why what I call the 'new later mothers' are absolutely right to delay motherhood.

"For one thing, they have a stronger family focus rather than trying to juggle priorities because they have achieved many of their personal and career goals.

"They also have more financial power because new later mothers have established careers and higher salaries.

And they they have more career experience and their management skills often translate directly into managing a household and advocating for their children."

Not only are they more likely to be married, they also tend to have a stronger network of close friends, she added.

Professor John Mirowsky, an expert on the issue from Texas University in Austin, believes the prime age for childbearing to maximise maternal health and longevity is between 34 and 40.

He said: "While younger women are more fertile and biologically fit, older mothers tend to be more mature and less likely to engage in risky behaviour, and they are more settled educationally, financially and emotionally."

The American claims are unlikely to end the age debate, however.

As well as the possibility of growing infertile, older mothers are said to face an increased risk of health complications during pregnancy, while their babies are more likely to have conditions such as Down's Syndrome.