Katie, 35, gave birth to baby Jett while on holiday in France last month, however she is said to have suffered complications and needed an emergency operation.
The mum-of-four apparently left hospital that night as the op went well and is recovering at home with her husband Kieran Hayler.
A source told The Mirror: "Katie was obviously really worried, as was Kieran.
"It's been a difficult few months, as she has been plagued by so many complications."
Katie by no means had an easy pregnancy with Jett and he was born prematurely in August while she was on a road trip in Europe with Kieran.
The tot had to stay in hospital for several weeks and had help with his breathing until he was strong enough to travel home to the UK with his parents.
Prior to that, Katie had admitted she was "having the worst pregnancy" due to a low iron count, sickness and exhaustion.
Since then, Katie has kept a fairly low profile but has shared cute pictures of Jett's crib and clothes with her fans on Twitter.
On Tuesday (24 September), Katie - who is also mum to Harvey, Princess and Junior - tweeted a picture of a cake she was eating, adding: "Baby Jett, he is as sweet as a cupcake xx"
Katie's rep confirmed to Reveal: "We can confirm Katie had a small operation but won't be making any further comment."