Watch the new mum show off her huge diamond ring.
While the couple is yet to formally comment on the exciting news, the pair have been very active with showing off the new sparkler that is sitting on Sarah's ring finger.
On Tuesday, the fitness trainer posted an Instagram story of the 3.02-carat diamond ring, captioning it: "No words."
The piece is from Anton Jewellery.
The couple first sparked thoughts of marriage when Kris referred to his partner as Sarah Smith.
Dannii Minogue's former flame had sent Sarah a bunch of flowers, while he was in the UK.
A hand-written card showed he had addressed the bouquet to "Sarah Smith" - to which she replied, "I f**king love you!"
Last year, the pair welcomed little Mila on December 5th.
At the time, the proud new dad gushed: "Last night at 10.15pm the world became a better place, the birth of our baby girl Mila Elle has been the most magical adventure ever."