Her husband Neil also shared his own post to announce the birth of their son, revealing the sweet meaning behind his name.
"Introducing Thomas Donald Elliot Varcoe. We call him Tom," he said. "He arrived during a 1 in 100-year flood with flippers for feet."
He added: "Donald was my father's name. He'd be proud."
It comes after Edwina revealed she was pregnant with her second child live on Sunrise in August last year, much to the surprise of her co-hosts David Koch and Natalie Barr.
"In developing news, news that will be developing news, news that will be developing for the next six months, we will be having another baby," she said during the segment.
"Due in February, and I tried to tell Molly and she was not terribly interested. I showed her the photo when she scrunched up and threw on the floor," she added of her daughter.
With their new bundle of joy finally here, Edwina's two-year-old daughter Molly is now a big sister, and the popular TV presenter hopes her second baby will be just like her.
"You know what you're in for and I'm not as worried or nervous this time around, because it all went quite well with Molly," she told The Australian Women's Weekly of her second pregnancy.
"Hopefully we have another Molly – they sleep well, and eat well, and it all goes to plan! Of course, that's not what babies do!"
Being a mother has given Edwina a whole new outlook on life, where she previously told TV Week how she wishes she'd made better use of that time instead of "sweating the small stuff".
"I think it's so rare for women to say, 'Hey, I'm good at this,'" she said, referring to the pressure women face as new mothers.
"But you know what? I'm a really good mum, and Molly's a really good baby. And we have a really happy family. That's such a huge achievement. I don't think 'old me' would have recognised that it's a big deal and a great thing to be able to accomplish."
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