Cheryl Cole took to Twitter to share her excitement at the prospect of the first 'Baby Aloud'.
The former X Factor judge, who had flown into Los Angeles on Wednesday night, wrote: "I just woke up to the news that there is to be a baby aloud!! This is so crazy. But amazing!!"
She later added, "Congratulations @nadinecoylenow. Can't believe you're going to be a mummy!!!!!!!!!!!"
Well wishes also came flooding in from other Girls Aloud members. Nicola Roberts tweeted: "@NadineCoyleNow Congratulations on your lovely news x", while Kimberley Walsh wrote: "Congrats on your exciting news!"
Sarah Harding is yet to comment on the pregnancy. On 10 August the singer shared a photo of herself in a car with the caption, "Road trip!!", so she may not yet have heard the news.
Nadine, 28, shared her pregnancy joy with the world by posting a picture of herself looking surprised on Instagram, with the caption, "I am having a baby!"
She then tweeted: "Just posted a photo", sending fans to the snap, which has since received more than 4,000 likes.
It is thought that the father might be her former fiancé Jason Bell. Earlier this year she reportedly rekindled her romance with the American footballer, 35, who she dated for over three years.
The couple announced the end of their one-year engagement in June 2011, with Nadine confirming the news via her Twitter account. "A few weeks ago Jason and I broke up," she told fans. "We are great friends and decided we are better this way. I'm in NYC working & I love all your support x."
But in March this year, the pair sparked speculation they had reconciled, with Jason travelling to the UK to see Nadine perform at the O2 Arena on Girls Aloud's farewell tour.