•The prime minister's wife announced the news on Instagram, saying she was hoping for a "rainbow baby" this Christmas.
•She wrote that, while she felt "blessed to be pregnant again", she had also "felt like a bag of nerves".
Carrie and Boris Johnson are expecting a second child, months after a miscarriage that left her "heartbroken".
The prime minister's wife announced the news on Instagram, saying she was hoping for a "rainbow baby" this Christmas.
She wrote that, while she felt "blessed to be pregnant again", she had also "felt like a bag of nerves".
Ms Johnson gave birth to the couple's son Wilfred in April 2020.
In a statement on Instagram, Ms Johnson wrote: "At the beginning of the year, I had a miscarriage which left me heartbroken.
"I feel incredibly blessed to be pregnant again but I've also felt like a bag of nerves.
"Fertility issues can be really hard for many people, particularly when on platforms like Instagram it can look like everything is only ever going well.
"I found it a real comfort to hear from people who had also experienced loss so I hope that in some very small way sharing this might help others too."
The couple married at a small wedding ceremony at Westminster Cathedral in May this year.
It was Mr Johnson's third marriage, with the prime minister having previously been married to Marina Wheeler with whom he had four children.
He did not have any children with his first wife Allegra Mostyn-Owen.
In recent years, several children have been born to prime ministers while in office.
Tony Blair and his wife, Cherie, welcomed their fourth child Leo in 2000, three years after the Labour leader's landslide victory.
A baby daughter, Florence, was born to David Cameron and his wife Samantha in 2010.