Keri Russell has revealed how tricky it was to wear a corset while pregnant when shooting new movie Austenland.

The 37-year-old stars in the quirky romantic comedy as a woman obsessed with the BBC production of Pride And Prejudice who travels to a Jane Austen theme park to find her perfect gentleman.

Dressed in black trousers and a black top with lace panels at the Los Angeles premiere of the film, The Americans actress said her costumes had to be made to accommodate her changing body.

"The corsets were pretty intense, especially when you're pregnant, but mine had expandable sides for every day my belly was growing. But there were a lot of angry ladies by the afternoon wanting more snacks.

"Lots of bonnets, lots of ribbons, lots of the costume people fixing stuff all the time."

Keri gave birth to her daughter Willa Lou Deary in December 2011. She is also mother to son River, five.

The star, who shot to fame on TV series Felicity, said her venture into period dramas involved some serious homework.

"We had to do some Regency-era manners classes which was hilarious, I was pregnant at the time and I am pretty sure I fell asleep. This guy talked for literally 18 hours, we were so bored and it was so hot. We learnt a lot about silverware placement."

Austenland will be in cinemas on September 27.