April 12, 2016 08:15 AM

Megan Fox‘s baby bump is here!

The actress, 29, showed off her third pregnancy at Monday’s CinemaCon in Las Vegas, where she promoted her new movie Teenage Mutant Ninja Turtles: Out of the Shadows. Evidence of the sizable bump poked through a black Versace minidress.

She posed for photos alongside her TMNT costar Will Arnett, turning just enough so that her baby bump was on full display.

Chris Pizzello/Invision/AP

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The star sported a big smile as she showed off her belly and talked about the new movie. But Fox said filming while pregnant isn’t easy.

“I’m always in the process of having a baby and looking like I didn’t have a baby,” she told PEOPLE at the event. “I was training. There was no access to healthy food on the set so I ended up losing weight because I was hungry all the time.”

Fox noted that her go-to food on set was a rice cake with almond butter and jelly. “That’s the healthiest thing you’ll find,” she said.

Todd Williamson/Getty

Sources confirmed to PEOPLE that Fox is expecting her third child. Fox has not openly discussed her pregnancy, nor the possibility that her estranged husband Brian Austin Green is the father, though a source with knowledge of the situation tells PEOPLE, “of course Brian is the dad! They never stopped loving each other and they will never stop being devoted parents to their boys.”

The actors are parents to sons Noah Shannon, 3½, and Bodhi Ransom, 2. The pregnancy came as a surprise for the couple who are “very excited” and are “continuing to work on their marriage and are living together again,” says another source.

Fox said her little ones don’t know much about their mom when it comes to the big screen. “They don’t watch television,” she said.

“I let them watch some movies, but I don’t let them watch my movies. They’re too grown up,” Fox told PEOPLE. “My kids are 3 and 2, so they’re not ready to know all that stuff.”

— Mark Gray and Char Adams

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