Speculation has been rife for the past month that the British actress and her Klaxons singer husband James Righton are expecting a baby together and the happy news was confirmed today (Fri) by Keira's representative.
Rumours circulated that the 29-year-old was pregnant when she 'steered clear from any champagne or alcohol' during an appearance on Sunday night at the Moet British Independent Film Awards.
Now her representative has confirmed the news to Elle UK although they added that no further details would be released.
On Sunday (Dec 7), Keira was presented with the Variety Award alongside her The Imitation Game co-stars Benedict Cumberbatch and Mark Strong.
She has also been nominated for Outstanding Performance by a Female Actor in a Supporting Role at both the upcoming 2015 Screen Actors Guild and the Golden Globe Awards for her role in The Imitation Game.
The actress - who has been with James, 31, since February 2011 - has made no secret of her desire to have children, but has previously insisted she would never give up her career to raise a family.
In 2012, she told Vogue magazine: "I don't want to deny my femininity. But 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."
Speculation about Keira's pregnancy was fuelled last month by a 'family source' who spoke to an American magazine.
"Keira and James are thrilled," the source told Star. "This wasn't planned, but that is how they wanted it."
In November, the source added that Keira is around 12 weeks pregnant and she has called on the help of her stylist to put together outfits that hide her growing baby bump.
Keira then added to the growing speculation by drinking nothing stronger than water while out in New York to promote Imitation Game.
She said her abstinence was due to an early alarm call the next morning as she was appearing on TV show Good Morning America, but her protestations have done little to stem the speculation.
"It's one way to ruin a party," Keira told the New York Times. "When they go, 'You have to get up at 5:30 in the morning the next day'.
"There are some really bad stories about people doing that and then going on these shows," she said, while pointing to her glass of water.
"You don't know what could come out of your mouth after a night out."