"I heard Jae say at the same time 'It's a boy!!!!!'. I burst into tears, he burst into tears and we got to meet our baby BOY💙"
The 31-year-old revealed the name of her new-born is Jax Stokes Woodroffe.
WATCH: Fitness Star Kayla Itsines’ Pregnancy Announcement
Kayla shared some pictures on Instagram including one of her three-year-old daughter holding her new baby brother.
"Healthy and quiet and as for Arna … even though she said she wouldn't if he was a boy… she absolutely LOVES him!!!" the mum of two wrote.
Itsines' sister Leah wrote, “My little love 🥺🤍 I can't wait to buy you a drum set my honey pieeeeeeee I love you so much already”.
Her fiance Jae Woodroffe also shared the exciting baby news on social media writing, "Meet our BOY Jax Stokes Woodroffe."
Shortly after announcing they were pregnant Jae and Kayla announced they were also engaged from their shared Instagram account.