"Last year I spent my 45th birthday in Perth, completing my final day of a 14 day hotel quarantine," she wrote.
"I’m typically not a huge “It’s my birthday” person (very uncharacteristic for a Leo, I know) but being alone on that day locked up in a tiny hotel room with no direct sunlight, access to fresh air and away from my kids and my man, I did make a promise to myself that I would thoroughly enjoy my next birthday to my best ability, if I was afforded the freedom."
This year, the mother-of-two made the best of being locked down for her birthday.
"Today I spent my 46th birthday in lockdown #6 in Melbourne, not ideal, but it sure as hell wasn’t nearly as bad as last year’s situation," she said.
"Whilst we were restricted, I was still fortunate enough to do a few of the things I had promised myself I’d do," she said.
"Like holding my little ones super close (I missed that so much last year)🥰 and enjoying my sweet home made cards from my kids."
Megan spent the day painting with water colour, having a dip in her pool, rollerblading around her neighbourhood, playing with her kids and making cocktails with Shaun.
"Something that I loved as a kid that I hadn’t done in 35 years and something that challenged me and pushed me out of my comfort zone," she said.
"And of course lots of kid cuddles, my favourite cocktail 🍹 made by my favourite person 🧔🏻and of course cake 🎂 (a Malteser ice cream one no less!)"
Dozens of Megan's celebrated friends wished the supermodel a happy birthday.
"Happy birthday Megs. ❤️ Rare air that double lockdown birthday, brava for the positivity," Zoe Foster Blake wrote.
Jen Hawkins commented: "Happy birthday beautiful!!" while Gorgi Coghlan wrote: "Happy birthday M. You’re such a talented artist! 🙌🙌."
Megan and former AFL player Shaun met in 2011, and although it wasn't love at first sight, after they got to know each other, those deep feelings began to grow.
"It was a slow burn," Megan admitted to the Australian Women's Weekly. "It wasn't that instant, see each other, fall in love, inseparable."
At the Megan was living in Sydney and Shaun was in Melbourne. They initially dated over Skype, and even though long-distance relationships can be a risk, it only solidified their undeniable chemistry.
"We'd start Skyping around 8 pm, then look at the clock, and it would be 4 am," she recalled.
The couple got engaged in 2017 and are yet to tie the knot, but in 2019 Shaun opened up about his marriage plans.
"There's just been so much on. Both of us are trying to find the time to focus on a wedding now that our lives are running smoothly. I can guarantee it'll be very small and intimate," Shaun told TV Week.
In May 2014, the couple welcomed their first child, a baby boy named River.
River's arrival, however, was bittersweet for Megan and Shaun as Shaun's father Tom lost his battle with prostate cancer a month before. Just 14 weeks after River's birth, Megan then lost her own dad, Alan to lung cancer.
In September 2017, the family of three became four when daughter Rosie was born.
Since welcoming their little ones, Megan and Shaun's love for each other has only grown.
"He’s such a loving dad and he’s so supportive of me. He’s very unaffected, and extremely humble," the mum-of-two said of her partner.