Teigen, who is married to singer John Legend, was updating fans via her Instagram stories on Thursday when she let the gender of her baby-to-be slip.
While talking about complications with her placenta she said, “It’s so weird because the baby’s really really healthy. He’s big.”
She quickly realized her mistake but laughed it off, “He’s probably, oops! That was stupid.”
Teigen posted the clip on her Instagram stories and captioned it, “Hahahahaha might as well tell you.”
Teigen and Legend already have a 4-year-old daughter and 2-year-old son.
They revealed they were expecting another child in Legend’s “Wild” music video in August, when she was seen holding her baby bump at the end.
She previously went through IVF for her two children but explained that this third pregnancy happened naturally and unexpectedly.