Why Australian women are waiting longer and longer to have kids.

How many women in their twenties do you know having babies? Depending on where in Australia you live, you might not know any at all.

While the average age of Australian women giving birth sits at 31.3, that doesn’t tell the full story. There are some affluent Sydney suburbs where more babies are born to women aged 35-39 than any other age group.

Research done by Macquarie University demographer Professor Nick Parr shows that with Sydney, women living in the eastern half of the city are markedly older when they give birth.

“You could draw a line from roughly Castle Hill in the north down to Sydenham in the south,” Professor Parr tells Mamamia. “Less than 30 per cent of the birth rate is due to women under the age of 30 everywhere east of that line.”

The director of the Australian Institute of Family Studies, Anne Hollonds, says there are “two Australias” when it comes to the age of women having babies.

“There are the women that are having larger families and starting younger,” she explains to Mamamia. “They’re probably more likely to be in the outer suburbs and they maybe have religious or cultural reasons for primarily seeing their role as a mother. I’m talking about families from other countries where the mother’s role is seen in more traditional terms.”

Then there are the women in the more affluent suburbs, with university degrees and professional jobs. They’re the ones whose average age for giving birth has risen so much in recent years.

Hollonds says there are a number of factors that explain the rise in age. It started back in the 1970s, with contraception becoming more widely available, and then continued over the next few decades as more women went on to tertiary education.

These are the things people who don’t want to have kids always hear. Post continues below.

“You’re going to want to see some value out of that investment,” she explains. “There are higher expectations as a result of that, in terms of your work prospects, but also income and lifestyle. So we’re more likely to want to delay that settling down, generally. The twenties have become more like an extended adolescence.

“That was happening before the house prices crept up to those extraordinary levels. But then I think the house prices kind of sealed it.”

Added on to that is work insecurity.

“Even if you’ve got a university degree you’re not guaranteed regular work in the way we used to think of it. You might be doing casual work for a long time. All of those things make it harder for young couples to make the decision to start having babies.”

Hollonds says Gen Y are fully aware that their fertility declines as they get older. But having babies just isn’t something that’s on their minds in their twenties.

“Nobody’s really thinking about it,” she says. “It’s not an issue that people really think about until they reach 30. That’s the anecdotal feedback that I’m hearing from that generation.”

This is one area in which Australia is well ahead of the US. It was only very recently that Americans began noticing an “astonishing demographic shift” – with, for the first time in history, women over 30 having more babies than younger women. Australia hit that milestone way back in 1999.

American researchers are trying to find reasons why the birth rate has dropped for women in their twenties. Economist Kasey Buckles believes it’s not just due to the economy, it’s also due to technology. She recently suggested to NPR that one of the reasons young people aren’t getting pregnant is that they’re preoccupied with smartphones, video games and social media.

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“Netflix and no chill,” she declared.

Hollonds agrees that what we’ve witnessed in Australia over the past few decades is a “very major shift”. Back in 1975, the average age of women giving birth was 25. But she says there are potential benefits to having babies at an older age.

“For children to have parents who have financial resources is not a bad thing,” she explains.

The biggest issue is that there’s now a smaller window for having babies.

“It’s got to be a project that you just focus on for those next few years, because you might miss out.”