The centre said a “procedural error” between April 2015 and November was to blame after sperm cells from one couple may have ended up with the egg cells from 26 other pairs.
Out of the affected women treated at the University medical Centre in Utrecht, Netherlands, nine have given birth, four are pregnant and 13 embryos remain frozen.
The centre has broken the terrifying news to patients and will be offering a DNA test.
Koro, dubbed ‘penis panic’ is a certified mass hysteria where men believe their members are in danger of vanishing. It’s more common in Africa and the Far East
“The UMC’s board regrets that the couples involved had to receive this news”
A statement from the clinic said: “The UMC’s board regrets that the couples involved had to receive this news.
“During fertilisation, sperm cells from one treatment couple may have ended up with the egg cells of 26 other couples.
“Therefore there’s a chance that the egg cells have been fertilised by sperm other than that of the intended father.”
In 2012 a mum in Singapore sued a clinic after she became pregnant with a stranger when a staff mixed up her husband’s sperm.
She suspected something was wrong when her baby was born with a different skin tone and hair colour to the couple.
And a sperm donor claims he could have fathered up to 100 kids by donating his cells via Facebook.