OH baby, what a year! WA has chalked up its biggest baby boom in history.

Final figures for 2011, to be collated this week, are expected to show the number of births topped 32,500, eclipsing the previous record of 32,139 babies born in 2008.

Nationally, the number of babies born in 2011 will top 300,000 that's more than the 250,000 born at the peak of the original baby- boomer generation in 1961.

Perth mother Marika Dimasi, whose second child Alyssa was among a dozen HBF member babies - one born in each month of 2011 - photographed by The Sunday Times, said she was considering another child.

"At the moment, I'm quite happy with two, but it's definitely an option to have more," she said.

Like a growing number of families, the parents of these 12 babies opted for private health insurance with HBF, with new figures from the WA insurer revealing a 165 per cent increase in the number of member births in the past two years.

The figures also showed an increase in caesarean births in the past few years, increasing from 13 per cent to 35 per cent of HBF births, which hit 5475 last year.

To the end of November, 30,126 WA babies had arrived in 2011, so if the monthly average of 2739 was achieved in December, it would mean 32,865 births last year an increase of 726 on 2008.

The rush of new arrivals, which is mainly a result of population growth in WA, will help the country hit another milestone in 2012, with the population reaching 23 million in July.

Latest Australian Bureau of Statistics figures show Australia's population grew 1.4 per cent in the past year, nearly 1 1/2 times the world average. "The debate over whether we want a big Australia or not is over we're getting one," social researcher Mark McCrindle, of McCrindle Research, said.

But women are waiting longer to have children, with the average age of mums rising from 29 to 30 between 2000 and 2009, a new report from the Australian Institute of Health and Welfare says.

"The proportion of mothers aged 35 and over also continues to rise up from 17.1 per cent in 2000 to 22.8 per cent in 2009," AIHW spokeswoman Associate Prof Elizabeth Sullivan said.

The number of births has been accelerating for a decade.The Howard government introduced the baby-bonus payment in 2002 after the fertility rate hit an all-time low of 1.7 children a family in 2001. Now the rate is more than two.

The ballooning of the new generation is is being mirrored at the opposite end as the original baby boomers reach retirement age.

"We will have more 65th birthdays next year than we've ever seen . . . we're looking at more than 200,000," Mr McCrindle said.