Boris Johnson’s fiancee, Carrie Symonds, has given birth to their baby boy.

A statement released by the couple said they had a “healthy baby boy at a London hospital earlier this morning”.

A spokeswoman for the prime minister and his partner said both mother and baby were “doing very well” after the birth in a London hospital on Wednesday morning.

The spokeswoman said: “The prime minister and Ms Symonds are thrilled to announce the birth of a healthy baby boy at a London hospital earlier this morning. Both mother and baby are doing very well. The PM and Ms Symonds would like to thank the fantastic NHS maternity team.”

The announcement came as speculation grew as to whether Johnson was going to take prime minister’s questions on Wednesday.

It is understood the prime minister was present throughout the birth, which took place in an NHS hospital in London.

Dominic Raab, the foreign secretary, will take the session going up against the Labour leader, Sir Keir Starmer, at the dispatch box for a second week in a row.

Johnson returned to frontline work on Monday after suffering from coronavirus and spending time in intensive care.

No 10 would not comment on Tuesday night who would be taking the question session in the Commons and earlier on Wednesday morning, leading to speculation they were leaving it until the final moment to make a decision.

However, the arrival of the baby is likely to be the reason No 10 was unable to provide any details on his appearance at PMQs.

Reacting to the news, Starmer tweeted: “Wonderful news. Many congratulations to Boris Johnson and Carrie Symonds.”

The health secretary, Matt Hancock, tweeted: “So thrilled for Boris and Carrie. Wonderful to have a moment of unalloyed joy!”

Symonds, 32, used to work as the Conservative party’s head of communications but now focuses on environmental and marine conservation issues. Her due date was described, when they announced they were expected, as “early summer” leading to speculation that the baby may have come slightly early.

The couple’s new son follows a recent tradition of babies in No 10 with David Cameron’s wife, Samantha, giving birth to their daughter Florence in 2010, and Cherie Blair giving birth to the Blairs’ fourth child, Leo, in 2000.

Johnson already has four children with his second wife, the barrister Marina Wheeler: Lara Lettice, 26, Milo Arthur, 24, Cassia Peaches, 22, and Theodore Apollo, 20.

The couple’s divorce was finalised in February after 25 years of marriage.

He also has another child fathered during an extra-marital affair while he was mayor of London. Johnson has repeatedly refused to disclose publicly how many children he has.

Symonds moved into Downing Street with him when he became prime minister and they are the first unmarried couple to live there.