Taking to Instagram, the BBG founder wrote: "20 WEEKS PREGNANT👼🏻💛"
"Tobi and I do not even have words to describe how happy and excited we are to bring you this news!
"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. Tobi Pearce has been SO supportive, SO EXCITED and so loving!"
"He comes home every day, hugs and kisses my stomach. He lays on my legs and asks the baby how it’s day was. He is at every scan and every appointment. I couldn’t ask for a better partner. Our family, well haha...you can just imagine - they are of course ABSOLUTELY OVER THE MOON EXCITED.
"I know you are already picturing the look on their faces when we told them.
"I know you ladies probably have 1 million questions ... but for now, let’s celebrate this amazing moment together as we are adding one new #bbg member in May next year. ❤️ We are SO happy to share this news and our journey with you! Thank you everyone!!"
The couple met in 2012 and have gone on to build a fitness empire worth an estimated $486 million.
Speaking to Women's Health, Kayla said: “I’ve wanted kids ever since I met Tobi and it’s something we have always talked about," the 27-year-old said. "It turns out that when we were ready it was just perfect timing. I think he will make the most perfect father, I’ve never seen him so excited about anything. He has already planned the funniest fluffy outfits for our winter baby and he talks to my tummy every morning and night."
“I am beyond excited to begin this new chapter of our lives together," Tobi said. "It’s definitely our largest achievement to date and I can’t wait to be a dad. Kayla has made me so proud as she has taken this on so naturally. It’s been a priority for me to support Kayla as much as I can during this time. I also couldn’t resist giving our baby a nickname, so for now it’s our Baby Muffin."