The United Nations has issued a stark warning about an unprecedented decline in world fertility rates, threatening global population stability. A new report from the UN Population Fund (UNFPA) highlights that hundreds of millions struggle to have their desired number of children, driven by the prohibitive cost of parenthood and a lack of suitable partners.

The UNFPA survey, covering 14,000 people across 14 countries, reveals that one in five individuals has not had or does not expect to have their ideal number of children. This alarming trend underscores a growing crisis in reproductive rights and intentions, prompting urgent calls for action to address the underlying economic and social barriers.

BBC.co.uk reports: The countries surveyed – South Korea, Thailand, Italy, Hungary, Germany, Sweden, Brazil, Mexico, US, India, Indonesia, Morocco, South Africa, and Nigeria – account for a third of the global population.

They are a mix of low, middle and high-income countries and those with low and high fertility. UNFPA surveyed young adults and those past their reproductive years.

“The world has begun an unprecedented decline in fertility rates,” says Dr Natalia Kanem, head of UNFPA.

“Most people surveyed want two or more children. Fertility rates are falling in large part because many feel unable to create the families they want. And that is the real crisis,” she says.

“Calling this a crisis, saying it’s real. That’s a shift I think,” says demographer Anna Rotkirch, who has researched fertility intentions in Europe and advises the Finnish government on population policy.

“Overall, there’s more undershooting than overshooting of fertility ideals,” she says. She has studied this at length in Europe and is interested to see it reflected at a global level.

She was also surprised by how many respondents over 50 (31%) said they had fewer children than they wanted.

The survey, which is a pilot for research in 50 countries later this year, is limited in its scope. When it comes to age groups within countries for example, the sample sizes are too small to make conclusions.

But some findings are clear.

In all countries, 39% of people said financial limitations prevented them from having a child.

The highest response was in Korea (58%), the lowest in Sweden (19%).

In total, only 12% of people cited infertility – or difficulty conceiving – as a reason for not having the number of children they wanted to. But that figure was higher in countries including Thailand (19%), the US (16%), South Africa (15%), Nigeria (14%) and India (13%).

“This is the first time that [the UN] have really gone all-out on low fertility issues,” says Prof Stuart Gietel-Basten, demographer at the Hong Kong University of Science and Technology.

Until recently the agency focused heavily on women who have more children than they wanted and the “unmet need” for contraception.

Still, the UNFPA is urging caution in response to low fertility.

“Right now, what we’re seeing is a lot of rhetoric of catastrophe, either overpopulation or shrinking population, which leads to this kind of exaggerated response, and sometimes a manipulative response,” says Dr Kanem.

“In terms of trying to get women to have more children, or fewer.”

She points out that 40 years ago China, Korea, Japan, Thailand and Turkey were all worried their populations were too high. By 2015 they wanted to boost fertility.

“We want to try as far as possible to avoid those countries enacting any kind of panicky policies,” says Prof Gietel-Basten.

“We are seeing low fertility, population ageing, population stagnation used as an excuse to implement nationalist, anti-migrant policies and gender conservative policies,” he says.