Posting an image of herself, pregnant and naked, Hayes wrote underneath the post that she was inspired to post the image after talking to a friend who was feeling a little discouraged and insecure about her new and changing body.
The 29-year-old revealed the image was taken just the day before she became a first time mum back in 2014, writing that although she was on the “rotund side” is was something she was happy she did and something she will cherish forever.
"A friend of mine messaged me today, slightly sad due to her weight gain as she is pregnant and is finding the rapid change of her body confronting. She wanted to know if I had felt similar, and what was normal for a new first time Mum, as forums are saying a million different things," the actress wrote.
"So, as today is #tbt, this nudie pic was taken the day before I went into labour. 48hrs later I was a first time mummy. As you can see, I'm totally on the rotund side, but having my make up done and a keepsake pic from extraordinary photographer Bradley Patrick, is something I'm glad I have celebrated and embraced."
Hayes continued by not only sharing her own experience, but left her followers with a reassuring message of support about their weight and the joy that surrounds pregnancy.
"Don't be down about your weight if your expecting- enjoy it as much as you can. It's not important, celebrate your baby growing... The weight might fall off, it might slowly come off or it might stick around. Once you hold that little baby in your arms, none of that will matter. I promise you it's all worthwhile," she wrote.
The young mum has been open and honest about her experience as a mother, only recently opening up about what it was like falling pregnant just six weeks after giving birth.
In sharing her experience, Hayes wrote about the difficulties in navigating both a newborn and a nearly pregnant body.
"Here I was. I’d just given birth, was so tired I couldn’t remember my own name and frankly, slightly depressed at a time I should’ve been happy (according to all my well-wishers who were kindly telling me this was going to be the happiest time of my life). And pregnant. AGAIN."
However, it didn't take the actress long to embrace her flaws and her strengths all as one, writing that she'll never be the mum who "sends her kid to school with the best tasting birthday cake" no will she"volunteer at the school canteen" but that's something she is totally okay with.
She may have her hands full with two young boys, but it's clear Hayes may subconsciously taking on another role at the moment: an honest and no-fuss mother that others can model their own experience off.
Watch: Women confess the time they felt like bad mothers.