"Hey Arnold, this is a selfie 📸 I am so proud of my body creating this beautiful baby boy 👶 Arnold, my tiny knitwear model, what a joy you are 😍😍," the former Biggest Loser trainer captioned the intimate picture.
Many commenters have praised the fitness star for her honest post.
"Showing what a real women looks like after birth," one wrote. "I had my baby 6 weeks ago and the pressure to get back in to shape is real. It's more important to focus on that amazing bundle of joy we created than getting our body back on track. That will happen over time."
"Thank you for sharing this photo," another commented. "I'm so sick of unrealistic expectations for new mums. You look so happy, healthy and vibrant, congratulations."
"Thanks so much for posting this picture @tiffhall_xo," one commented. "You look absolutely beautiful! I remember two weeks after having my baby I was so upset because I didn't look like all these other models,wags and Insta famous women did 2 weeks postpartum. Looking back I see how silly it was for me to compare with some other ppl. I wish I had seen your picture after having my bundle of joy, definitely would've been more kind to myself."
"So precious. I love this real pic. What an role model you are," posted one."
The adorable Arnold is Tiffiny and hubby Ed Cavalee's first child.