A leading fertility expert is urging couples to start a family at a younger age amid fears of a growing over-reliance on science and technology.
Dr Richard Fisher, co-founder of the country's largest infertility services provider, said one-third of women receiving treatment for IVF were over 40.
"And we treat most of them because they are over 40, not because of an underlying medical condition. The longer you delay, the less your chances of conceiving. If you have the opportunity to conceive younger you should take it."
Couples beginning relationships late in life and women's focus on career - combined with the ease of access to fertility treatments - are tempting couples to wait until later to try for a child.
But Dr Fisher, head of Fertility Associates, warned that delaying pregnancy was the leading cause of infertility.
The chance of conceiving a child drops from 22 per cent at the age of 30 to 6 per cent at 40.
"The fact people are trying to get pregnant later is a social construct, a result of the environment we live in and expectations."
Dr Fisher said the tendency was to move towards technological solutions.
Fertility doctor Guy Gudex, Repromed Auckland's medical director, said many couples were surprised that those solutions did not always work.
"There's always that thought - if all else fails, of course there's always IVF at the end. It doesn't always work."
Dr Gudex said the reality was many women in their 40s could not be helped at all, and the government funding cut-off for fertility treatment was 39.
With at least a one-year waiting list in Auckland, that meant couples needed to think about conceiving earlier.
In 1990, the number of women having babies between their mid-30s and mid-40s was just over 5000, according to Statistics New Zealand.
Last year, that figure had almost tripled to more than 13,600.
Dr Fisher said GPs needed to warn their female patients about their chances of falling pregnant.
"I think GPs should be saying to patients in their early 30s, 'Do you understand the issues about delay?"' he said.
"Most people who come to see us are astonished at their low chance of conceiving. They say they'd never heard about it."
Tony Townsend, deputy president of the Royal New Zealand College of General Practitioners, said doctors were definitely seeing more women who were trying to get pregnant later in life.
If women were thinking about trying to conceive, doctors were encouraging them not to leave it too late, he said, but often couples had a misplaced confidence.
"There's a bit of denial ... They [patients] think, 'I know about that risk but it's not going to happen to me'," Dr Townsend said.
Michelle Collyer, chief executive of Fertility New Zealand, a support organisation for couples going through fertility treatment, said couples who left it late and struggled to conceive faced a tough, emotional process.
It was a shock, and people felt very vulnerable, Ms Collyer said.
"The main comment from our members is that, if they had the information [about the difficulty of conceiving] earlier, they would have made an informed choice."