Chrissy Teigen was updating fans on her Instagram stories when she let the cat out of the bag.
Teigen was talking about complications she was having with her placenta, when she said: ""It's so weird because the baby's really really healthy. He's big."
The 35-year-old television personality and model immediately realised her mistake, but laughed it off saying: "He's probably, oops! That was stupid."
She later posted the video to her Instagram feed with the caption "HahahahahaI might as well tell you."
Teigen is married to singer John Legend, and they previously announced that she was pregnant in John's music video for Wild back in August.
They already have two kids- daughter Luna, who is 4 and son Miles, who is 2.
The couple previously went through IVF for their first two kids, but this happened naturally and unexpectedly, according to the pair.