The first time mum and her boyfriend, Justin Scott, welcomed a son Bobby yesterday afternoon, confirming the news via her Twitter page.
32-year-old Kimberley tweeted: 'Our beautiful baby boy Bobby arrived yesterday afternoon,' adding: 'he's perfect.'
Amazingly, Kimberley gave birth exactly on her due date of September the 4th, with Walsh confirming her friends predicted this to be the case. 'My friends have joked that my baby would arrive on time because I'm always so punctual' she joked, 'and he did!'
This is the second Girls Aloud baby, with Irish star Nadine Coyle having given birth to a daughter Anaiya six months ago.
Cheryl Cole was quick to congratulate her former bandmate and friend, writing: 'He really is. He's perfect!'
According to baby name website She Knows, the name Bobby means 'famed, bright and shining.'
They add that people with the name Bobby 'have a deep inner desire for a stable, loving family or community, and a need to work with others and to be appreciated.'
We're sure that Kimberley and partner Justine will provide him with just that. Congratulations to both parents!