Millions of poor urban children are more likely to die before their fifth birthday than those living in rural areas, according to a UN study out on Tuesday that challenges popular assumptions behind the global urbanisation trend.
The UNICEF research found not all children in cities benefited from the so-called urban advantage - the idea that higher incomes, better infrastructure and proximity to services make for better lives.
"For rural parents, at face-value, the reasons to migrate to cities seem obvious: better access to jobs, healthcare and education opportunities for their children," said Laurence Chandy, UNICEF director of data, research and policy.
"But not all urban children are benefiting equally; we find evidence of millions of children in urban areas who fare worse than their rural peers."
Although most urban children benefit from living in cities, the study identified 4.3 million globally who were more likely to die before age five than their rural counterparts, and said 13.4 million were less likely to complete primary school.
"Children should be a focus of urban planning, yet in many cities they are forgotten, with millions of children cut off from social services in urban slums and informal settlements," said Chandy in a statement.
About 1 billion people are estimated to live in slums globally, hundreds of millions of them children, according to the UN children's agency.
A decade ago, the world officially became majority urban, and two-thirds of the global population is expected to live in urban areas by 2050, according to the United Nations.
"We applaud UNICEF for putting numbers around a problem that will only get more serious as more and more families move to cities," said Patrin Watanatada of the Bernard van Leer Foundation, which works to promote early childhood development.
"Cities can be wonderful places to grow up, rich with opportunities – but they can also pose serious challenges for a child's healthy development."
Poor transport links and access to health clinics, parks as well as growing air pollution and stressed care-givers can exacerbate city living for children, said Watanatada.
Improved walking and cycling infrastructure, affordable housing and transportation and polices targeted at supporting children and those who care for them could help ease life for urban families.
ICLEI, a global network of more than 1,500 cities, towns and regions, said disasters were more likely to impact the most vulnerable in cities, including children."Children are disproportionately affected by gaps in urban services, especially when it comes to water, sanitation, air quality, and food security," said Yunus Arikan, head of global policy and advocacy at ICLEI.