Carrie Symonds and her fiancé Boris Johnson have announced the birth of their first child together, a "healthy baby boy".
A spokeswoman for the couple said that both mother and baby are "doing very well", after the birth this morning at a London hospital.
She added: "The PM and Ms Symonds would like to thank the fantastic NHS maternity team.”
Johnson returned to No. 10 on Monday followed a period in intensive care, having contracted coronavirus. Symonds is also believed to have suffered from symptoms of the disease.
Symonds announced she was expecting a baby with her partner in “early summer” and became engaged to her fiancé last year. Prior to the outbreak of Covid-19, Johnson had announced his intention to take paternity leave. Given present circumstances it is unclear whether this remains the case.
Dominic Raab, the foreign secretary, will stand in for Johnson at today’s prime minister’s questions.
Congratulatory messages to the pair came from across the political spectrum.
Chancellor Rishi Sunak posted on Twitter: "Great to hear Downing Street is getting a new resident. Congratulations to @BorisJohnson and @carriesymonds on the birth of their son."
Matt Hancock, the health secretary, tweeted: "So thrilled for Boris and Carrie. Wonderful to have a moment of unalloyed joy!"
Sir Keir Starmer, the new Labour leader, said: "Wonderful news. Many congratulations to Boris Johnson and Carrie Symonds."
Across the border, Nicola Strugeon, Scotland’s First Minister, wrote that: "Some good news - sending congratulations to Carrie and the PM. And wishing health and happiness to the wee one."
Symonds and Johnson moved in to Downing Street in July, and adopted a dog together called Dilyn.
In an interview during the general election, when asked how many children Johnson had, he replied: "I love my children very much but they are not standing at this election. I'm therefore not going to comment on them."