British Prime Minister Boris Johnson's partner Carrie Symonds on Wednesday gave birth to a "healthy baby boy" in a London hospital, a spokesman for the couple said.
The news came as a surprise, as Symonds, 32, was not thought to be due for several weeks, but she was said to be doing "very well".
The birth comes just days after Johnson, 55, returned to work after being admitted to hospital with coronavirus, including three nights in intensive care.
"The prime minister and Ms Symonds are thrilled to announce the birth of a healthy baby boy at a London hospital earlier this morning," the spokesman said.
"Both mother and baby are doing very well.
"The prime minister and Ms Symonds would like to thank the fantastic NHS (state-run National Health Service) maternity team."
The announcement explains why Downing Street officials were reluctant to confirm that Johnson would appear at his weekly question and answer session with members of parliament.
Foreign Secretary Dominic Raab, who deputised for him during his illness, is expected to take his place later on Wednesday.
Johnson is believed to have at least five children, including four with his second wife, Marina Wheeler, from whom he split in 2018.
He has been publicly dating Symonds, a former head of communications for the Conservative party, since early 2019.
They announced in February that they were getting married and expecting a baby "in the early summer".
On her Instagram page, which is set to private but details of which were reported in the media, Symonds revealed they got engaged at the end of last year.
Johnson only returned to work on Monday, two weeks after being discharged from hospital for an illness that he said "could have gone either way".
Symonds had moved out of their Downing Street flat before he became ill, but later reported having symptoms of coronavirus herself. She recovered at home.
She has kept a low profile as the "first girlfriend", largely keeping out of the election campaign last December that saw Johnson win the best result for the Conservatives since the 1980s.
An avid environmental campaigner, after leaving the Conservative party she worked for an ocean conservation charity.