She and partner Mark O'Shea shared the good news with their friends and family as they were inundated with messages of congratulations.
Earlier this week, Michelle posted a photo of her baby bump (right) as she revealed that she "couldn't wait" to meet her tiny bundle of joy.
Expose producer Debbie O'Donnell was among the first to congratulate a delighted Michelle, who's said to be doing well after the birth.
She said she was "absolutely thrilled" for the couple and described it as "amazing news".
Her comments were echoed by 3e's weatherman Deric Hartigan who extended a "massive congrats" to Michelle and Mark.
There's obviously something in the air at Xpose - Michelle's presenter pal Karen Koster is due her first baby with hubby John McGuire in December.
Donegal native Michelle has been taking it easy since leaving the TV3 entertainment show in May, focusing on becoming a mum.
By coincidence, she had been covering for Aisling O'Loughlin's maternity leave after she gave birth to her second baby with partner Nick MacInnes.
And she's clearly been excited about the new arrival as she kept her Twitter followers up to date throughout her pregnancy.
Michelle said she plans on taking a good deal of time off as she puts her career temporarily on the back burner.
"I want to be able to bond with the baby and build the relationship," she said.
"You can't put your life off because of jobs. I just always wanted to be a mum and I thought, 'Whenever it's the right time I'll take my blessings'."
The former model, who used to present a show on Phantom FM, said she feels extremely lucky to have become pregnant so easily.
"I'm feeling great. I've been so blessed, I've had the best pregnancy. I was never sick and only now I'm getting tired in the evenings," she said.
"But all along it's been amazing. I was more worried that I wouldn't be lucky enough to get pregnant because so many people struggle to.
"Some people do take it for granted and I was never one of those because I love children so much. Once I found out, it was that initial thing of going, 'Oh my God, am I ready?'"
Michelle previously fronted a popular music programme on Phantom and she also worked as a DJ in many of Dublin's top clubs.