The Girls Aloud star revealed she is expecting a baby by sharing a picture with her followers on her Instagram page announcing the happy news, but has yet to confirm the father's identity.
The sepia-tinged snapshot shows an excited looking Nadine with the words, "I am having a baby. Xx', emblazoned across the image.
Her legions of over-excited fans rushed to congratulate her and tell her what a good mother she is going to make.
One posted: "OMG! Actually crying! You will be an amazing mummy, I don't mind babysitting for you at all ❤ love you so much ❤ (sic)"
Another wrote: "Congratulations Nadine! You're going to be an absolutely amazing Mum ❤❤ (sic)"
Nadine is thought to have got back with her partner of three years, American footballer Jason Bell, after they were pictured together in March this year.
The couple announced their one-year engagement was over in June 2011, but rumours of a reconciliation began to circulate when Jason jetted to the UK to watch her perform with Girls Aloud at London's O2 arena earlier this year.
Nadine, 28, previously dated 'Dallas' hunk Jesse Metcalfe and had a brief romance with club promoter Waz Ashayer last year.
The 'Sound of the Underground' hitmaker will be the first of her former bandmates - who found fame on 'Popstars: The Rivals' in 2002 - to become a mother.