The Les Miserables star, 33, gave birth to baby Jonathan in March (16), her first child with husband Adam Shulman.

As a result of being a new mother, Anne has been limiting her workload so she can spend time with her little one.

However with the star's new movie Colossal, which she filmed in the early stages of her pregnancy, debuting at the Toronto International Film Festival (TIFF) earlier this month (Sep16) she has been thrust back into promotional activities.

And she admits she finds it very difficult when her work commitments keep her away from her son.

"I’ve done like little pockets of press, a little thing here, or a quick photo shoot," she told U.S. website "Yesterday was a day where I was gone all day, came home, spent time with him and then had to go out again at night. And I gotta say, it was hard.

"And I don’t even know of the word to describe it, please help me out if any of you can, because I was so happy to show the film and so gratified that it was showing at TIFF. And I all wanted to do was stay home with my baby."

The actress said even though she was aware of how lucky she was to be one of the world's biggest film stars, she could not help but feel bad about missing out on time with her son.

"I’m just aware how (much of a) privilege this tear (sic) is," she explained, but added, "I only have negative words to describe this experience."

Although the star is back on the promotion trail to for Colossal, in which she plays Gloria, a woman having a mental breakdown, she is yet to return to a film set since giving birth.

She does however have two projects in the early stages of production, a movie adaptation of actress Jenny Mollen's collection of essays, Live Fast Die Hot, and a female fronted remake of Ocean's Eleven, titled Ocean's Eight.

Colossal, which also stars Jason Sudeikis and Downton Abbey star Dan Stevens, premieres in the U.S. on 29 September (16).