The Avengers star reveals she suffered the clumsy incident a day before she was due to head to Georgia to film TV movie Confirmation, and it was only when she arrived on location that the new mum realised the seriousness of her injury.

She says, "I just fell in my apartment and it was so silly.

"I was leaving the next day to go shoot a movie in Savannah and the smart me decided to strap my newborn on to my chest and go to Savannah. I didn't know it was broken. It was like a solid day of walking, solid day of re-breaking my bone."

Smulders was signed to star as lawyer Harriet Grant opposite Kerry Washington in the Anita Hill biopic for America's HBO network, but she was subsequently replaced by Salt actress Zoe Lister Jones after pulling out of the film.