The I Hope singer thanked God for her news, tweeting late on Sunday night.
"Yes I am having a new lovely baby children are such a blessing and I'm grateful to god for my new little gift xx" Rebecca tweeted to her over 800,000 followers.
She included in her tweet a picture of two swans in the shape of a heart and the words: "There’s a little heart beating next to mine."
The 27-year-old also tweeted a photo of a sonogram alongside a poem by an unknown author.
Rumours had been swirling for several weeks after Rebecca fainted towards the end of a live performance on ITV’s Loose Women.
Yes I am having a new lovely baby children are such a blessing and I'm grateful to god for my new little gift xx pic.twitter.com/qm2XMBQ0Y3— Rebecca Ferguson (@RebeccaFMusic) April 13, 2014
The singer, who recently released her second studio album Freedom, had just finished singing her single All That I’ve Got when she fell to her knees.
Co-host Myleene Klass rushed to the 27-year-old’s side and put her in the recovery position.
At the time the Liverpool songstress had tweeted that she was feeling unwell.
"Still laid up in bed, dunno what this bug is but it's getting shaken off big tomorrow xxx," she wrote on Twitter.
Rebecca Ferguson collapses on Loose Women
Rebecca already has two children, Lillie May and Karl.
Although she has not announced who the father is, Rebecca revealed to The Mirror late in 2013 that she was dating a friend whom she had known for years.
Rebecca finished second on The X Factor in 2010, ending up in the final with One Direction but lost to Matt Cardle.
She later went on to date One Direction's Zayn Malik, who is now engaged to Little Mix's Perrie Edwards, for four months, although the pair later split after admitting they found the media attention difficult to deal with.
last date of the tour ... until my holiday then afterwards recording another album in sunny LA I love my life amazing tour!!! thank you xxx— Rebecca Ferguson (@RebeccaFMusic) April 13, 2014
The soul singer finished her UK tour on the same day as announcing her pregnancy. She also revealed she will be soon heading to LA to start work on her third album.
"last date of the tour ... until my holiday then afterwards recording another album in sunny LA I love my life amazing tour!!! thank you xxx" she tweeted.