The star looked as gorgeous as ever on the show, choosing to wear a pair of wide-leg Zara jeans, a striped top from Joanie and a pair of patent Topshop heels to make her announcement.
WATCH: Alex Jones announces third pregnancy on The One Show
She was visibly nervous as she told co-host Ronan Keating about her surprise pregnancy, saying: "I feel really nervous all of a sudden... it just seems like a good time to share some news with everybody - and the crew in the studio for the first time!
"Lockdown has been anything but predictable, and we've had some really unexpected news. Baby number three is on the way!"
Lou-Lou Scallop Trim Top, £32.00, Joanie Clothing
Alex also revealed that she is having a little girl, who will be a sister to her two sons Teddy and Kit.
Wide-Leg Cropped Jeans, £27.99, Zara
The TV presenter also revealed the news on her Instagram page with an adorable photo of her family. In the black-and-white snap, the couple beamed at the camera, with Alex holding her youngest son. Sweetly, Teddy held aloft a sign which simply read: "Coming soon… Baby number 3."
Alex's loyal fashion stylist Tess has previously told us how the star has altered her wardrobe since becoming a mum.
After she returned to The One Show after her maternity leave with Kit, she told us: "Alex is back from maternity and is hosting The One Show after having her second son Kit so we wanted to shake things up a bit with regards to her style. She has totally got back to her pre-baby body so she makes most things look good."
As for when she's at home with her children, not much changes according to Tess! "I know that she's like me - with two small children she loves comfort, practicality and anything you can throw in the washing machine," she said.
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