Shay Mitchell Reveals She Filmed 'Something From Tiffany's' While Pregnant (Exclusive)

The actress was pregnant with her daughter, Rome, while shooting the rom-com.

Shay Mitchell is thankful for the Something From Tiffany's costume department.

ET's Cassie DiLaura spoke to the mother-of-two at the rom-com's premiere on Tuesday, where she revealed that she was "very pregnant" while shooting the film. Joking about her ever-expanding pants, Mitchell said filming while pregnant with baby No. 2 was "fun."

"It was definitely very fun. I was also very pregnant. So, it was fun," Mitchell, who shares daughters Atlas, 3 and Rome, 5 months, with partner Matte Babel, quipped. "The ever-expanding costume pants I was wearing; it was a great time."

Busy on and off screen, Mitchell, who welcomed her second daughter in June, told ET it's been "special" to see her girls interact.

"They are amazing. And it is really special to see both girls, and now interacting with one another and now the holidays, of course," she shared. "So, that'll be fun hearing their Christmas lists. It's ever-expanding. It's really fun."

As for what her home will look like during the holidays, the Pretty Little Liars alum had one word: "Mayhem."

"But I love that. I think just messes, spilled eggnog, milk -- everything," Mitchell said. "I mean, the more chaotic the better."

The Christmas-time film stars Mitchell, Kendrick Sampson and Zoey Deutch, who plays a woman whose life gets upended when an engagement ring that was for someone else leads her to the person she's meant to be with. And while Something From Tiffany's is pegged for the holidays, Mitchell said it's a movie viewers can watch year-round.

"It's just an awesome movie for this season for any time around the year," she gushed. "It's a great little love story."

She also praised the film's executive producer, Reese Witherspoon, calling the actress a "boss."

"She is a boss," Mitchell maintained. "She's amazing. Somebody I definitely look up to."

Something From Tiffany's premieres Dec. 9 on Prime Video.