Theresa May has provoked hilarity in the House of Commons by mistakenly congratulating Jeremy Corbyn "on the birth of his granddaughter".
The comment came after the Labour leader "welcomed" the news that one of his MPs - Conor McGinn - had delivered his own daughter at home.
The prime minister admitted she had "completely missed" the point, as proceedings were held up by laughter.
She blamed cabinet colleague Patrick McLoughlin for the wrong information.
Mr Corbyn joked that this was "ungallant".
During Prime Minister's Questions, Mr Corbyn began his appearance by referring to McGinn, who had to help his wife give birth on their living room floor at the weekend when their baby came earlier than expected, helped by what he called a "crash course in midwifery over the phone with a 999 call-handler".
Mr Corbyn asked: "Could I take this opportunity of welcoming Neasa Constance McGinn and hope that the evidently effective course in midwifery undertaken my by honourable friend, the member for St Helens North, isn't a sign to the government that we believe in downgrading midwifery training."
Mrs May responded: "First of all, can I congratulate the right honourable gentleman on the birth, I understand, of his granddaughter."
With Labour MPs querying what she had said - and letting her know that Mr Corbyn had not recently become a grandfather - proceedings stopped as those on all sides of the House laughed, including the prime minister.
To more hilarity, Mrs May added: "No? I'm sorry. In that case I completely missed..."
When MPs had regained their composure, she said: "In that case, can I just say that perhaps one should never trust a former chief whip?"
She turned to look at Conservative Party chairman Mr McLoughlin, sitting to her right, who used to serve as chief whip.
He laughed and mimed his throat being slit.
Mr Corbyn replied: "It's a bit unfair to blame a former chief whip for some little bit of confusion - very ungallant. Can't we just admire the member for St Helens North on his work?"
Later in the session, in response to another Labour MP's questions, Mrs May congratulated Mr McGinn on the birth of his daughter.