Box revealed in her post that she was expecting her child after undergoing IVF with an anonymous sperm donor.
She heaped praise on her "amazing" IVF doctor, who helped her achieve her dream.
"After a series of egg retrievals and freezing, last year I started the process to become pregnant via an anonymous donor," she said.
Box gave birth to Trixie, whose father is former Ironman Grant Kenny, in 2013.
The pair split after a brief romance in 2012 but are reportedly on good terms, with Kenny regularly visiting his daughter in Melbourne.
The TV personality said she was "blessed" to be having a "much-wanted sibling" for her daughter.
"I know the value of this miracle because I have seen first hand the heartbreak, tears and sacrifices so many women and couples suffer on their IVF journeys and my heart goes out to those who are facing that pain and struggle," Box wrote in her emotional post.
"It is not lost on me that I am one of the lucky ones."
News
A Gold Coast family has been left “devastated” after receiving an anonymous letter from a “concerned neighbour” complaining about noise made by children.
News
Stop Adani activists targeting global giant Siemens, trying to force the company to sever ties with the Indian mining company, have just received a big shock.
Crime
The mother of two baby girls who died after being pulled from a hot car has appeared in court, as the first person in Queensland to be charged under the new...
Politics
This is the human face of Qld Health’s inability to pay. After eight overdue invoices, she says it was a call to the Minister that finally got the ball rolling.