“Grey’s Anatomy” star Katherine Heigl has motherhood down pat because she already has two daughters, but she is pregnant with her first biological child--a son--so she is new to adjusting her pregnancy with her work.

The actress is currently filming the upcoming CBS legal drama “Doubt.” The biggest challenge of the job is not the acting range, but her character’s wardrobe choices. Heigl told PEOPLE that they are doing their best to hide her baby bump while she portrays lead character Sadie Ellis.

“Now I feel like [viewers are] only going to be watching that, and [they’re] just going to be like, ‘Oh, she’s hiding her baby bump in this scene,’” she said. “But yeah, I am. That’s what I’m pretty much doing… in every scene.”

Heigl revealed that the costume crew initially wanted to dress Sadie up in figure-flattering clothes, but her growing baby bump prevented them from doing so.

“We’re working really hard to try to hide [my pregnancy], and it’s a challenge,” Heigl said. “Because every day my body changes a little bit more.”

“We started out with really high hopes of like, fitted, pencil skirts and those really great Victoria Beckham dresses, and that became impossible pretty quickly,” she continued.

Heigl’s character Sadie is a smart attorney working at a boutique firm. Her weakness is her growing attraction to her client Billy Brennan (Steven Pasquale), who has been accused of murdering his girlfriend, according to TV Guide.

Try as Sadie might to keep her relationship with Billy strictly professional, Sadie finds herself unable to do so. “She's trying to separate herself emotionally,” Heigl explained, “but struggling with it. We're tying to keep it relatable and human.”

Heigl will co-star in the legal drama together with “Orange is the New Black” star Laverne Cox, who will play transgender attorney Cameron Wirth.

“I’m really, really grateful to have a job as an actor,” Cox told Variety of her new role. “Four years ago, I was standing in February of 2012 in New York City with an eviction notice in my hand…so I’m just really happy to have a job.”

Other cast members include Steven Pasquale, Dulé Hill, Dreama Walker, Elliott Gould and Kobi Libii.