The news was originally reported by Page Six this week, who have said that the British actress is over three months pregnant and “celebrating” motherhood.
"Keira and James are thrilled. This wasn’t planned, but that is how they wanted it"
The 29-year-old star, who married James at an intimate French wedding last year, sent the rumour mill into overdrive recently when she avoided alcohol at an awards event.
An American magazine then quickly claimed that Keira was already three months pregnant with the couple's first baby, revealing that it was a happy surprise for the pair.
A source said: "Keira and James are thrilled. This wasn’t planned, but that is how they wanted it.
"Keira and her stylist have been putting together looks that hide her growing bump."
The actress has just finished working on her latest film, Everest, and is reported to be planning a break from acting when she gives birth to her first child.
The source explained: "She will be able to relax and settle into family life in London."
However Keira previously stated that, when she does start her family, she has no intention of becoming a 'stay-at-home mum'.
She said: "Would I want to be a stay-at-home mother? No.
"On the other hand, you should be allowed to do that, as should men, without being sneered at."
Congratulations to Keira Knightley and James Righton!