“Mornings,” the Keeping Up With the Kardashians star, 20, captioned the image donning white bath robes with several girlfriends.
As well, she shared a glimpse of her belly while wishing her BFF Jordyn Woods a happy birthday.
“Yesterday was cute,” she captioned the image with Woods and a giraffe. “Hope you had the happiest of birthdays Jordy. Love you forever ever and beyond..”
Reportedly, the couple expect their baby to arrive in February.
“They started telling friends a few weeks ago,” said a source. “The family has known for quite some time. She is REALLY excited and so is Travis!”
Another insider added: “It is an unexpected but completely amazing turn of events that she could not be more excited or thrilled about.”
“Everyone is overjoyed for her,” added the insider. “This is the happiest she’s ever been.”
Kylie has been dating the Goosebumps hitmaker since earlier this year after splitting from her on-again-off-again beau, rapper Tyga, in April.