Researchers from the University of Otago are investigating whether New Zealand is more affected by infertility than other high-income countries.
The study probing the topic follows research in Otago and Southland that suggested the prevalence of infertility issues in New Zealand could be greater than in other comparable countries.
Researchers were analysing general health data as well as obvious fertility risks, such as sexual health, from the Ministry of Health's 2014/15 survey, to establish what factors could be associated.
Researcher Antoinette Righarts is working on the study, titled The burden of infertility in New Zealand, along with senior researcher Professor Wayne Gillett and biostatistician Andrew Gray.
Righarts led the initial studies in Otago and Southland as part of her PhD research back in 2015.
"We found quite a high prevalence in infertility - one in four couples - and the research was quite consistent," Righarts said of the study.
"Five, six years ago the statistic that people used to quote was one in six."
It was believed that in 2014/15 high-income countries like New Zealand, Australia and the United Kingdom had an infertility rate of one in six.
Righarts said this was "more often than not" caused by people delaying getting pregnant.
She suspected there was a widespread lack in knowledge around fertility in New Zealand.
A lot of women didn't know what age their fertility began to decline or what the average changes of conception per cycle was.
"People don't openly talk about not being able to conceive. Whereas it's very visible when someone has conceived."
"People's perception is coloured by what they've seen and their expectations."
Early findings suggested there was no difference in Māori and Pakeha men and women.
"It's significant that Māori have just as high a burden of infertility as non-Māori," Righarts said.
Righarts' 2015 investigation looked at the prevalence and understanding of infertility issues among women in the region as well as how many couples were using services such as IVF.
It involved interviewing Southland and Otago woman between the ages of 25 and 50, and found more than a quarter, or 25.3 per cent, of women who had tried to become or had been pregnant, had experienced infertility.
These results indicated Kiwis could face a greater prospect of fertility struggles than in other developed countries.
However, Righarts said it was important to note the difficulty in comparisons.
Other studies conducted overseas used different definitions of infertility.
The current study Righarts is leading would be comparable with a recent study in the United Kingdom.
The official definition of infertility was when a woman had unsuccessfully tried to conceive for at least 12 months or needed medical help to do so.
Along with specific sexual health data, the research also considered more general living conditions - income, education and age.
Juanita Copeland, vice president of Fertility New Zealand, was well aware that New Zealand was "up there" in the world in terms of the number of people requiring treatment for infertility.
The initial study highlighting infertility rates down south showed the issue "didn't discriminate", Copeland said.
"It seems to affect every aspect of our community in terms of socio-economic situations, levels of education, ethnicity - all of that stuff."
Copeland hoped the research would increase the level of discussion around infertility, as well as boost funding for treatments such as IVF in the future.
This would raise some important questions around why so many Kiwis struggled to conceive, she said.
"On the face of it you would tend to think we have a pretty wholesome lifestyle here in New Zealand," Copeland said.
"But age is sort of the biggest factor in infertility and I guess the broader scope is that life and living is more expensive these days.
"People are leaving family building until much later than is biologically ideal."
Fertility New Zealand was working in conjunction with Righarts' team and would release some of the data established through the study in Fertility Week next month.