The star, 34, announced the lovely news with a pic of her newborn's tiny hand holding her own, revealing that the pair had welcomed a second girl. They're already parents to three-year-old daughter Belle.
'We've been blessed with the safe arrival of a baby girl. Our family is now complete 🌸👶🏾,' Katie wrote alongside the adorable image.
Fans have rushed to congratulate the couple on their new family member, with one writing: 'Aww huge congratulations ! So delighted for you and your beautiful family.'
'Awww congratulations just in time for Christmas 👶🏽💖🎄' another added.
'Congratulations to all of you ❤️,' echoed a third. 'Such a beautiful picture!'
The pair have not yet shared the baby name they've chosen for their bundle of joy.
Katie first revealed that she was pregnant again back in June, during an exclusive interview with HELLO! magazine.
'Becoming a mum has enriched my life in ways I never imagined and I feel so thankful to be experiencing that again,' she said to the title at the time.
Katie and Richard did not announce the gender of their baby, although many fans guessed that they were expecting a girl after Katie wore a rather telling dress to her baby shower.
The TV presenter previously shared a snap of herself wearing a picture of both a blue and a pink version of an outfit from her own collection, asking her followers: 'Which one do you think I'm going to be wearing to my baby shower in 2 weeks?'
When she subsequently appeared wearing a slightly different dress, but in a clearly pink shade, many predicted that another daughter was on the way.
'Does that mean it's a girl as you wore a pink dress? As a while ago you said you wondered if you were going to wear pink or blue to your shower?' one queried, whilst another wrote simply: 'Congratulations on another little girl!'
Turns out the speculation was correct - we're thrilled for Katie, Richard and big sister Belle!