The Girls Aloud singer surprised fans by sharing her happy baby news via Instagram on Thursday morning (15 August).
Nadine posted a picture of herself looking surprised alongside the caption: "I'm having a baby x."
She added no further comment.
Nadine hasn't announced who the father is yet. It was rumoured earlier this year she had rekindled her romance with American footballer Jason Bell after he was pictured at a Girls Aloud ten-year reunion show, but she never confirmed this. The couple had been engaged until they called off their relationship in 2011.
The 28-year-old will be the first member of Girls Aloud – which includes Cheryl Cole, Nicola Roberts, Kimberley Walsh and Sarah Harding – to become a mum.
Among those congratulating Nadine via Twitter was former TOWIE star Amy Childs, who wrote: "Congratulations to you babe."
Northern Irish singer Nadine had hinted she had big news to share earlier in the day, tweeting: "Just went on a major following spree. Random celeb following spree. Ps I have Craic (irish slang for news, gossip, fun) for you."
Congratulations to Nadine!
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