Many women noted that they found Sarah's pregnancy body to be motivation to work out and live a healthy lifestyle.
One fan wrote: "I'm completely inspired to go to the gym first thing in the morning. You look absolutely gorgeous."
Another said: "You look absolutely lovely. Hats off to you for being fit and taking care of yourself!"
Another added. "If I ever have children, I'm inspired by you to treat my pregnancy the very same way. I'm sure James will be amazing! Congratulations."
Others compared their figures to pregnant Sarah's pregnancy body, with one woman writing: "10 days before giving birth?! Lord Jesus help us all! I look like this after dinner."
Sarah told news.com.au she's stayed in shape throughout her pregnancy by doing 'light prenatal training for the past month' and pilates, mainly working out her arms and legs.
She joked: "I can't really do abs these days!"
She said her diet consists of brown rice, quinoa, veggies, chicken and steak. But she said she also allows herself to indulge in her pregnancy cravings.
She said: "I love In N Out Burgers and mint chip ice cream."
Some of her 1.1 million Instagram followers have expressed concern over her small size at such a late stage in her pregnant.
One commented: "I really pray her baby is healthy. If she's 8 months that baby is very much looking undersized."
Another added: "Wtf she is 8 months pregnant no freaking way."
But Sarah said she's happy and healthy.
She said: "These days it's seems like everyone has something to say, especially on social media. Most are very positive and I try to ignore any negative comments. My doctor says the baby is healthy and that's all that matters to us.
"We are so excited for our baby boy to arrive! I'm almost done with his nursery and am counting down the days. We can't wait to be parents!"