"I’ve known for a long time. It’s been really hard for me to keep it a secret," Tortorella, 29, told ET's Leanne Aguilera at the ATX Television Festival in Austin, Texas, on Saturday. "I’ve known for a few months."
"She is such an incredible mom and I got to spend some time with Luca on set this year and he’s just such an incredible kid," Tortorella marveled. "She's been talking about having another baby for years and I’m so excited that she gets to have one."
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Hilary Duff Slays in a Black Bikini While Enjoying a Beach Day With Ex Mike Comrie and Son Luca
"It’s what we all are looking for in one way or another, and she's got it. She's preggers,"I love pregnancy so much. I have the fever so hard right now… I can't wait to start having kids. I’m so excited."
While Tortorella told ET that it was personally difficult to keep Duff's pregnancy under wraps, the show also had to come up with creative ways to hide her burgeoning baby bump while filming season five.
However, he said that the show's creator, Darren Star, didn't know "until after we wrapped, honestly."
"I think he was the last one to find out of all of us," Tortorella said, laughing. "[But] timing-wise, it’s perfect. She’s going to have the baby [and] we don’t start shooting until next year. It’s perfect!"