"Huge Congrats to you and Sam Pang! 👌🏻👌🏻" he joked in the comments section.
Megan Gale wrote, "Yes! Beautiful news beautiful Mama ❤️" while Emma Watkins penned "Congratulations ❤️❤️"
Belinda Russel wrote "Congratulations!! ❤️", Georgia Love added, "Huge congratulations Tiff and Ed!!!!" and Shaynna Blaze said "Well you hid that well!! Congratulations 👏👏"
She's right; Tiffiny did a magnificent job of hiding her growing belly for the last few months and left many fans shocked when she revealed her pregnancy yesterday.
But scrolling back through her Instagram, it's easy to see how she kept us all in the dark for so long.
Recent photos of the mum-to-be show her bundled up in loose hoodies, jackets and jumpers that keep her belly out of sight – lest fans notice her bump.
She also snapped plenty of photos sitting down with one of her legs propped up, which partially obscured her belly, or even posing with her back to the camera.
Tiffiny also made sure to post plenty of promotional photos from her activewear brand TXO, which appear to have been taken before she started showing.
All of these clever tricks worked together to keep fans in the dark about her pregnancy until Tiffiny was ready to announce it herself on Sunday.
Now fans and friends alike are wishing the 37-year-old well as she embarks on her second pregnancy journey after a difficult first time.
The stunning trainer welcomed her first son, Arnold, in 2017 but spent her entire pregnancy basically bedridden with hyperemesis gravidarum.
The condition is quite rare and causes severe and persistent nausea and vomiting during pregnancy and lasted for all nine months of Tiffiny's first pregnancy.
WATCH: Tiffiny Hall's Ultimate Abs Workout
"I put on 30kg, I was sick the whole time right up until my last contraction and all I wanted was sausage rolls," she told news.com.au at the time.
"My pregnancy didn't go to plan, but it delivered me a healthy baby. I just embraced it and was proud of what my body achieved."
Unfortunately, her pregnancy struggles didn't end there and during her labour the umbilical cord became wrapped around Arnold's neck, leaving Tiffiny and Ed terrified.
Fortunately, Arnold was delivered safely and the little family of three have spent the last few years enjoying life as a trio.
Now Tiffiny and Ed are excited to be giving their son a little brother or sister after keeping the pregnancy a secret for so long!
This article first appeared on our sister site, Now to Love.