The pop star announced the happy news on Twitter.com, writing, "Yes I am having a new lovely baby children are such a blessing and I'm grateful to god for my new little gift."
She posted her news alongside a cute photo which proudly announced: "There's a little heart beating next to mine".
She also shared a second image of a baby's sonogram, alongside a open:
It read: "Running errands and talking on the phone, I am pleasantly reminded that I am not alone.
"Little tiny hands, a precious rounded knee, pushing and twisting that no one can see.
"Oh sweet child kicking up your heels, it is our little secret that only I can feel.
"I look forward to your birth, when I can kiss your skin. But for now I will just smile as I feel you play within."
Rebecca is already a mother of two children, Lillie May and Karl, from a previous relationship. The father of her unborn baby is not known, but the star has revealed in recent interviews that she is dating a man she has known for several years.
The announcement comes two months after Ferguson appeared to faint on U.K. daytime TV show Loose Women after performing her track All That I've Got.
The collapse came after Rebecca tweeted that she hadn’t been feeling well.
She wrote: ‘Still Laid up in bed, dunno what this bug is but it's getting shaken off big tomorrow xxx.’