"Our little ray of sunshine Frankie (Francesca) O'Keeffe snuck into the world very quickly... and a month early... on Monday night. She's tiny (less than 2kg) but she's a trooper and we're so in love 💕🌞," she wrote with a gallery of pictures post birth.
As previously reported by WHO, the journalist made her pregnancy announcement with a snap her pet dog.
Piotrowski appeared to be holding a baby onesie branded with an NBA team logo.
"Not sure of the gender... but the NBA team is not negotiable. Baby O'K coming July '18," she captioned the cute picture.
Piotrowski and her Publican husband married just more than six months ago in a lavish New York City garden wedding.
Piotrowski has been working on the Channel 9 network for eight years.
All the best to the happy couple!