Testing has found that many Nigerian men are unaware they are raising children who are not biologically theirs, a national daily claimed.
It included tales of men who had discovered they were not the biological fathers of their children, often years later.
The Vanguard credited the three in 10 figure to an unnamed forensic geneticist. (Note: The story also said it was "at least four out of 10 men".)
But is this claim about the scope of "scandalous family secrets" backed by evidence?
2012 story had same headline
The name of the sole interviewee wasn't provided. But he gave an even higher figure, saying 50% - five in 10 - of men tested at his lab were not the biological fathers of their children.
What is paternity fraud?
In a 2007 paper, researchers at the University of Birmingham said misattributed paternity was sometimes called "paternity fraud". The term, they said, "suggests that the mother (and possibly her lover) knew about the true paternity and deceived the man for financial gain".
The "fraud" may be discovered inadvertently during medical treatment or uncovered when there were doubts about paternity, the paper said.
We asked experts about the state of the data on paternity fraud in Nigeria.
'No data on paternity fraud, it's personal'
Chris Olashunde, the Nigeria representative for UK-based DNA testing firm EasyDNA UK, told Africa Check that there wasn't data on paternity fraud in Nigeria because it was "a personal thing".
"Most of the paternity tests in Nigeria are done due to mistrust or to resolve conflict. But some do it simply for immigration purposes," Olashunde said.
"I cannot say whether or not it's up to 30% because there is no data to prove that in Nigeria. The best you can find is the rate of failure of paternity tests at DNA testing centres."
'Only those who have done testing'
Ayodele Adeniyi runs Lagos-based testing firm Paternity Test Nigeria. He said about a third of the men tested at his firm found they hadn't fathered at least one of their children.
"I would say the claim that three out of 10 Nigerian men are not the father of their children is correct," he said.
But, he added, "that is if we are considering only those who have done paternity testing".
Not nationally representative
Paternity test data from testing centres cannot be taken to represent the entire country, Dr Isiaka Olarewaju, the director of household statistics at Nigeria's National Bureau of Statistics, told Africa Check.
This is because the data would be skewed. "For a ratio to apply to Nigeria, the sample has to be random and nationally representative," he said. "The people that go for the DNA test in many cases are educated and aware that such tests exist, and they can afford it. They cannot represent the whole country."
A survey would be needed to determine the extent of paternity fraud in Nigeria, Olarewaju said. This would ideally be a sample of at least 6,000 households, with about 1,000 from each of the country's six geopolitical zones.
Most countries do not have data on paternity fraud
What about another claim in the Vanguard's article, that Nigeria is second only to Jamaica for paternity fraud?
A 2005 paper, Measuring paternal discrepancy and its public health consequences, put paternal discrepancy at 0.8% to 30%, giving a global median of 3.7%.
The researchers examined the titles and abstracts of peer reviewed scientific literature on the topic from 1950 to 2004. One of their conclusions was that "no clear population measures of paternity discrepancy are currently available".
Mark Bellis of the Centre for Public Health at the UK's Liverpool John Moores University was one of the paper's authors.
Bellis, who is also a professor of public health at Bangor University in Wales, told Africa Check he doubted there was a reliable global ranking on the prevalence of paternity fraud.
"I am not aware of any detailed studies of paternity fraud in Nigeria (only a few opinion pieces) so I cannot comment on the quality of these data," he told Africa Check.
"It is however highly unlikely that there is a reliable international league for paternity fraud as the necessary studies or data do not exist in the majority of countries."
Conclusion: No data supports 30% paternity fraud claim in Nigeria
In an article on "paternity fraud", a national newspaper in Nigeria said 30% of the country's men were not the biological fathers of their children.
A number of experts told Africa Check there was little reliable data on this in Nigeria, apart from individual testing centres. But a statistician at the national statistics office said data from testing centres was unlikely to represent the whole country.
For this, a survey of a nationally representative sample drawn randomly would be required.
We therefore rate this claim as unproven.