Two of Justin's ex-girlfriends have also reacted to the news, sending their congratulations on social media.
Sofia Richie (now Grainge), who dated Justin briefly in 2016, wrote: "Ahh!! Congratulations," on Justin and Hailey's announcement post.
While Caitlin Beadles, who was Justin's first girlfriend in 2008, wrote: "congrats, happy for y'all!"
Justin and Hailey announced the news on their respective Instagram pages. They both showed a video of the couple kissing at a vow renewal ceremony before zooming in on a close-up of Hailey's stomach.
Hailey's representative has confirmed the model is just over six months pregnant.
Justin, 30, and Hailey, 27, got married in 2018 in a secret ceremony after dating on and off for two years.
Justin mum has also shared how her "heart is full" following the news Justin and his wife Hailey are expecting their first child.
"BABY BIEBER IS ON THE WAY!!" Pattie Mallette, 49, wrote on Instagram. "I'm gonna be a GRANDMA!! CONGRATULATIONS @justinbieber and @haileybieber!! My heart is so full. What an exciting new adventure. Love you so much!"
She then spoke in a video, saying, "So I have been waiting for this day and now that they have shared it I can finally celebrate with y'all. Oh my gosh, I'm going to be a grandma - oh my goodness... praise God."
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