The model and TV star, 34, is expecting her third child with Grammy-winning singer John Legend, 41.
The couple are already parents to daughter Luna, four, and son Miles, two.
The couple have previously revealed the pregnancy was unexpected because it was the first conceived without IVF.
Teigen previously appeared to accidentally reveal they were expecting a boy while updating fans on her pregnancy.
She referenced the child as “he”, saying: “It’s so weird because the baby’s really, really healthy. He’s big. He’s probably – oops. That was stupid.”
Realising she had said more than she intended, Teigen covered her mouth with her hand before continuing to discuss her pregnancy.
She shared a clip of the slip on social media and captioned it: “Hahahahaha might as well tell you.”
Teigen has since confirmed the news, sharing a picture of the ultrasound of the baby and wrote: “Hi my sweet strong boy.
“You are working so hard, I promise it’ll be worth it!!!”
— chrissy teigen (@chrissyteigen) September 17, 2020
Teigen has discussed her previous struggles while pregnant, telling fans “my placenta sucks”.
She said: “It’s always been kind of the bad part of my pregnancies with Luna, with Miles. It just stopped feeding him. It stopped taking care of him.
“I was stealing all his food because I was getting huge but he wasn’t getting big at all, so he had to come out early and Luna had to come out early. I was induced both times.”
Teigen, who said doctors have put her on “serious bed rest”, said the baby is “growing beautifully”.
“Everything’s good,” she added.
“I’m feeling really good, but my placenta’s really, really weak and it’s causing me to really bleed a lot. So basically, it’s just pretty high risk.
“This poor thing has been through so much already. We just have to get my placenta healthy again, and that means not moving so I’m on complete and total ‘don’t get out except to pee-pee’ bed rest.”
Teigen and Legend confirmed they were expecting a third child in August, announcing the news in the music video for Legend’s single Wild.
