The model gave birth to a baby girl – her fifth child – on Monday, 4 August.
So far she hasn't revealed the tot's name.
Over the weekend, besotted mum Katie told fans on her YouGossip account: "Me and Kieran are so in love with our gorgeous little miracle baby girl. It's completed our family."
She accompanied her heartfelt post with a super cute picture of her child's teeny tiny feet under a blanket.
Katie didn't have the easiest of pregnancies. Just a few days after learning she was expecting, she found out Kieran had been having an affair with her best friend.
Heartbroken Katie vowed to divorce her cheating husband at first, but in recent weeks it's clear she is willing to give their relationship another chance.
And perhaps alluding to the past, she posted a cryptic message online yesterday. It read: "One of the happiest moments in life is when you find the courage to let go of what you can't change."
Another cryptic message shortly after read: "People come and people go. The best will stay."
Katie, 36, and Kieran, 27, married in January 2012 following a whirlwind romance. They welcomed their first child together, Jett, that summer.
Katie is also mum to three other children – Harvey, Junior and Princess – from previous relationships.
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Stars who welcomed babies in 2014:
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