Rachel Riley and Pasha Kovalev are expecting their first child together.
The Countdown star announced the news on Instagram and Twitter using a picture of herself cradling a baby bump on the set of the Channel 4 game show, with the letters on the board spelling out “R TINY MATE”.
She wrote: “Pash and I have a conundrum for you… you have till December to work it out!
“We’re over the moon excited.”
Maths whizz Riley, 33, and Russian dancer Kovalev, 39, have been together since 2014 after they were partnered in the 2013 series of Strictly Come Dancing.
Riley started dating Kovalev after splitting from her husband and fellow Oxford University student Jamie Gilbert in 2013.
Earlier this year Kovalev announced he was leaving Strictly after eight years on the show.
Current Strictly champion Stacey Dooley was among those celebrating the baby news, tweeting “congrats!!!” to Riley.
Pointless star Richard Osman aped the Countdown conundrum challenge by writing “GANCINUORTSLAO!!!!!” instead of congratulations on Twitter.