"Welcome to the world little Poppy Krasenstein. Born on the 22nd of July 3:59pm 6 pounds 7. Mum and Bub are absolutely crushing it," he wrote.
A number of MKR alum took to the comment section to congratulate the new parents.
Chris Rillo wrote: "Congratulations! What a gorgeous little bundle."
While Sal Caputo added: "Oh what a beauty!"
Poppy has already been nicknamed an "MKR baby" as Chloe fell pregnant while the show was being filmed.
John – who entered the competition with mum Lisa – explained: “During filming, Chloe took
a couple months off work and she came over to Sydney so we could keep trying for a baby."
The Perth couple said they almost lost hope when Chloe didn't fall pregnant in the first year of marriage.
"Chloe and I got married almost three years ago and we started trying straight away," John said.
“I think a lot of people have the same problem and I think it's just not talked about a lot," Chloe said.
"You never know if it's going to be you that's going to have a problem until you try.
"I think, as well, [it puts a] strain on your relationship...because it takes a bit of the fun out of things. I think that was something that we weren't prepared for, I guess, because we never thought we'd have those issues.
“After a while, every month, it gets very, very sad.”
After nearly three years of trying, when Lisa and John were accepted onto the 10th season of MKR, Chloe decided to take some time off work and travel with them around the country as they filmed the show.
"It was good not to have the baby as the focus as soon as MKR came up," Chloe says.
"It was kind of like, that's our focus now...we don't have to think about [getting pregnant] all the time.”