The hilarious celeb couple, who celebrated their fourth wedding anniversary on September 14, shared the news on Tuesday (local time) with the help of their one-year-old daughter Luna.
In an Instagram video, model and cookbook author Teigen points to her stomach and asks Luna, "What's in here?" "Baby!," the toddler replies. Teigen captioned the video, "It's John's."
Teigen and Legend have been open about their fertility struggles over the years. After tying the knot in 2013, they welcomed baby Luna three years later with the help of IVF. Teigen has also spoken candidly about having post-natal depression.
"I lost all interest in everything," she told US Weekly in September. "I couldn't get out of bed. I kept all my pyjamas in the pantry because I didn't want to go upstairs."
The Cravings author has also spoken out about her desire to have more kids with 'All of Me' singer Legend.
"We want a lot of kids," said Teigen. "When it happens, it happens. For us, it's hard because he's on the road so much and I'm working. People think it happens so easily, but the stars really have to align to have a baby, and it is a little miracle. So when it happens - we will be so happy."