Chrissy Teigen has accidentally revealed she and her husband John Legend are expecting a baby boy.

The model and TV presenter, 34, slipped up on her Instagram while talking about her pregnancy. 

The pair are due to welcome their third child and are already parents to Luna, 4, and Miles, 2.

In a post about her pregnancy, she said: "My placenta sucks. It's always been 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. He had to come out early, Luna had to come out early. I was induced both times.

"It's super weak. It's so weird because the baby's really really healthy, he's big."

She then realised her mistake and covered her mouth in shock. 

Teigen became engaged to Grammy-winning singer Legend, 41, in 2011 after four years of dating. 

The duo later married in Como, Italy in September 2013. 

One fan commented: "Best gender reveal ever."

And another added: "This is how you gender reveal, folks."