Prime Minister Boris Johnson and his wife Carrie are expecting their second baby, she has announced.
In the Instagram post, Carrie also said she had a miscarriage earlier this year.
She wrote: “Hoping for our rainbow baby this Christmas.
“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.”
She added: “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.”
A “rainbow baby” is a child born after a miscarriage, stillborn or neonatal death.