The singer took to her Twitter page to announce the happy news to her fans.
Sam wrote: ‘Me and Craig are proud to announce we are having a little girl... A special thank you to @miracleprogress xxxx.’
It seems that not everyone in the Bailey household was happy with the news.
Sam posted a hilarious photo of her son, Tommy, pouting after finding out he was getting another sister rather than a brother.
Sam captioned the photo with: ‘Tommy not so pleased that he is having a baby sister!!! Lol.’
Sam is also mum to a daughter, Brooke. The new addition will be the star's third child with husband Craig.
Speaking to a UK magazine prior to revealing the sex, Sam revealed that she and husband Craig had been thinking hard about names for their third child.
‘We've chosen one to match our children's names now. We've got Brooke and Tommy so we can't have anything too odd. We're conscious about name-matching.’
Sam became the 10th winner of The X Factor in December and recently released her debut album- of which features covers of her favourite love songs- earlier this year.