According to a source, the former glamour model discovered she was expecting during her luxurious family holiday in Cape Verde.
The insider told The Sun: ‘It's not something they had planned this soon after Jett, but they're still delighted. The news came as a complete shock.’
‘Katie's already in her second trimester so has been pregnant for nearly six months without even realising it. She's due later this summer.’
‘Unlike her other four pregnancies, she's yet to have any cravings and is not showing much, either.’
Kate sported a slightly rounded tummy in the series of holiday snaps she shared on Twitter, but aside from that the mum of four has managed to keep her pregnancy relatively concealed.
Katie and husband Kieran Hayler were also spotted shopping at Mothercare upon their arrival back in the UK, adding further fuel to the fire that she is indeed expecting.
Katie is already mum to son Harvey (10) from her brief relationship with footballer Dwight York and son Junior (8) and Princess (6) from her marriage to Peter Andre.