Christmas has come early for Adelaide-based fitness blogger Kayla Itsines.

Taking to social media, Ms Itsines and her partner Tobi Pearce announced they will be expecting their first child.

"Tobi and I do not even have words to describe how happy and excited we are to bring you this news," the 27-year-old wrote alongside the video, which revealed she's 20 weeks pregnant.

"If you don't know already, I come from a big Greek family. FAMILY is always what comes first in my life. To be able to start my own family with the person I love most in this world is just an absolute dream come true."


The video, which showed the pair during an ultrasound, has been viewed more than 1.6 million times in the past hour, and received over 8000 comments.

"@tobi_pearce has been SO supportive, SO EXCITED and so loving! He comes home every day, hugs and kisses my stomach," she wrote of her partner.

"He lays on my legs and asks the baby how its day was. He is at every scan and every appointment. I couldn't ask for a better partner."

Some of her 10 million followers commented on her post, congratulating the couple on the exciting news.

"Congratulations you guys! This is so beautiful," one person wrote.

"This is the best news ever! Congratulations!," another said.

Earlier this year, the pair announced their engagement by showing off a sparkling ring on Instagram.

"It was during a family dinner which included some close friends, and I really wasn't expecting it so my reaction was of total shock and happiness," she said. "It was really romantic as Tobi was on one knee.


"We have lived together for over four years, we have two beautiful dogs, an amazing business … and to top it off … Tobi got down on one knee last week and asked me to marry him … in front of my family!," she wrote on social media.

"I obviously said YES to spending the rest of my life with my very best friend. We have been together for five-and-a-half years now, and I cannot wait for the many years and memories to come … I love you so much."

In October, Itsines was announced as the richest young woman in the country.

Along with her fiance, the pair came in at fifth and sixth place in the 2018 Financial Review Young Rich list, thanks to their staggering combined wealth of $486 million.

Ms Itsines, 27, is now officially Australia's richest young woman, and the couple are the wealthiest self-made 20-somethings in the country.