A national snapshot of mothers and babies shows 60 per cent of women who gave birth in Canberra were aged 30 or older, the second-highest proportion in Australia.

The information comes from a new report, Australia's Mothers and Babies 2006, to be published today by the Australian Institute of Health and Welfare.

The average age of first-time mums in Australia is 28, while one-fifth of women who gave birth in 2006 were aged 35 or older, up from 15 per cent in 1997.

Caesarean sections make up almost one-third of births in Australia.

Canberra has a high proportion of older mothers and relatively few young ones: only 2.5 per cent of mothers one in 40 were teenagers, the lowest rate in the country.

The ACT's figures are distorted because about 16 per cent of new mothers in Canberra are NSW or other interstate residents.

Despite this, the territory still leads the nation when it comes to multiple births, with 2.1 per cent of ACT-resident mums having twins or multiple babies.

Women who gave birth in Canberra were also shy of hospitals. The ACT had the second-lowest proportion of women 92.6 per cent giving birth in hospitals.

Another 7 per cent chose to have their babies in birth centres, a figure higher than any other part of Australia except South Australia.

The report also sheds light on birth trends across the country.

Of Australians who gave birth in 2006 by caesarean, 84 per cent had done so previously.

Nationally, there were 9750 more births in 2006 than in the previous year, the report shows.

Of 2006's babies, 8 per cent were pre-term (less than 37 weeks' gestation), compared with 7 per cent in 1997. with AAP