The news was confirmed by Thea's family on Instagram, sharing a photo of the vlogger wearing a black-and-white top.
"To all Nicole’s friends and supporters it is with great sadness that I have to inform you that Nicole and her son she and Boga named Reign sadly passed away on Saturday morning," the caption said. "Also Nicole pre-schedule [sic] a few YouTube videos and [her boyfriend Global] Boga has made the decision to allow them to be aired."
Thea and Boga were expecting a son together.
"As a family we ask that you give us privacy because our hearts are truly broken and we are struggling to cope with what has happened," the social media post continued. "Thank you her mum RIP My beautiful baby girl Nicnac and my grandson Reign, I will miss you for the rest of my life until we meet again in eternal heaven."
Thea's cause of death is unclear, and reps did not immediately respond to Fox News' request for comment.
Thea, who has more than 75,000 YouTube followers, had been very open about her pregnancy, often sharing videos of her experiences as a mother-to-be on her YouTube channel. Her most recent video featured footage of the vlogger taking a milk bath and posing for a pregnancy photoshoot.
The news of her pregnancy was also shared on Instagram in April.
"We can’t hide this any longer, secrets out.. GOD gave us the biggest blessing yet. I’m finally creating a beautiful little human inside of me," she wrote at the time. "Can’t believe this bubba will be half of me and half of the loml."
Thea called her boyfriend "the best support EVER."
"We are already obsessed with you our little miracle baby. Thank you for choosing us to be your parents and best friends," the post finished. "Mummy and Daddy can’t wait to love, hold and cherish you for ever and ever."