Growing financial uncertainty and an ageing population mean families are now just as likely to be made up of a couple with no dependent children as a couple with children living at home.

By 2026 the couples without children at home will have overtaken those with children as the most common type of family in Australia, a new report on family composition shows. But this is likely to accelerate should the economic turmoil worsen.

Financial concerns such as big mortgages and job uncertainty are among the main reasons couples delay having children or have fewer than they would like. 

The report, by the Federal Government and to be published today, suggests financial concerns such as big mortgages and job uncertainty are among the main reasons couples delay having children or have fewer than they would like.

"There are more younger couples delaying having children or not having children at all," says the report, Australian Families 2008.

An ageing population also means there are more "empty nesters" than in the past.

People aged between 30 and 34 are now more likely to have children than those aged between 25 and 29. Those with children say they are having fewer than they would like.

"Although the number of women having only one child or no children is increasing, more Australians would prefer to have four or more children than to have no children or only one child," the report says.

Whether someone can afford to have children is as common a consideration as whether their partner would make a good parent.

The Government uses information on the changing composition of families to plan for schools, hospitals, community centres and other infrastructure.

And fewer children means fewer family members to care for ageing parents.

Couple-only households started to grow in 1976 and in 30 years have risen from 28 per cent to 37 per cent of all families.

At the same time the number of couples with dependent children dropped from 48 per cent to 37 per cent. The proportion of one-parent families rose from 7 per cent to 11 per cent in the same period.

Those trends will cross over in the next few years, meaning that couples without dependent children will be the most common type of family by 2026.

The rising age of first-time parents is contributing to the trend, the report shows.

Nearly half the women, 41 per cent, having their first child are now aged over 30 compared with 28 per cent a decade ago.

Better assisted reproductive techniques and more widely available contraception means the number of mothers over 40 has increased at the same time as the number of teenaged mothers decreased.

More women aged between 40 and 44 are having children now than at any other time, although the overall numbers remain low.

Despite concerns that the so-called baby bonus would increase the number of teenaged mothers, the reality has been the opposite. The number of women under the age of 20 having children halved between 1977 and 2007.

But the decline only brings the teenaged birth rate into line with the average in Organisation for Economic Co-operation and Development countries. It is still higher than in France and Spain but lower than in New Zealand and the United States.

What do you think? Will the economic downturn affect your decision to have a child, or have more children? Discuss this with Essential Baby members.