The British actress and her husband Alessandro Nivola welcomed daughter May last month (Jan10) - but Mortimer feared she'd harmed the baby during her pregnancy after a particularly traumatic evening in a Japanese restaurant.
Mortimer was so desperate to impress her Leonie co-star Shido Nakamura and the film's director and producer, she gulped down what was put in front of her.
She recalls, "I was trying so hard to be charming and have them think I was cool, and they were all so impressed by me because I ate some sort of weird Japanese spinach."
The star then opted to try a piece of sushi: "I took a bite and it was raw chicken! I kid you not. It was raw chicken dipped in raw egg, which was apparently some delicacy. And the weirdest thing, instead of stopping there I kept eating it. Then I got home and cried on the phone to Alessandro, 'I've killed our baby!'"