"People don’t think they are going to get pregnant [at that age], so you get a spike of unintended pregnancies" ... Elizabeth Sullivan

"People don’t think they are going to get pregnant [at that age], so you get a spike of unintended pregnancies" ... Elizabeth Sullivan

The average age of Australian mothers is still rising, but not as rapidly as it was a few decades ago, new statistics reveal.

In 2010, the average age of women having their first baby was 28, slightly up from 27.9 the year before. In 2001, first-time mums were 27.5 on average.

The latest data released by the Australian Institute of Health and Welfare (AIHW) also revealed that the proportion of older mothers (classed as 35 and over) has continued to increase. In 2001, 17.5 per cent of mums fit into this age group, but a decade later, that number was 23 per cent.

"We've seen a drop in teenage births over the last 10 years, and we have continued to see this increase in over-35 and over-40s in terms of women of that age having their first birth," AIHW spokeswoman Elizabeth Sullivan told AAP.

Sullivan told news.com.au that many women aged 40 and over would have been surprised by their pregnancies.

“People don’t think they are going to get pregnant [at that age], so you get a spike of unintended pregnancies among women who thought they were past it,” she said.

“You still need to use contraception in your 40s.”

Sullivan also noted that “fewer than 50” women aged 50 or older had had children in Australia in 2010.

One woman, considered the oldest first-time mum in Australia, had her first child at age 60. Sullivan said it was “highly likely” the woman would have used assisted reproductive technology of some kind.

Other facts from the AIHW study

  • In 2010, 294,814 women gave birth to 299,563 babies.
  • In 2010, the average age of all mothers was 30, compared with 29.2 in 2001.
  • There were 562 women aged 45 and over who gave birth, accounting for 0.2 per cent of mothers.
  • Available data suggests assisted reproductive technology is used by about four per cent of women who give birth.
  • Smoking while pregnant was reported by 14 per cent of all mothers and 37 per cent of teenage mums.
  • In 2010, 22.4 per cent of women who gave birth were obese. This proportion ranged from 19.3 per cent in the ACT to 24.6 per cent in Tasmania.

AAP and staff writers