Anne Hathaway "didn't tell anybody" she was pregnant.
The 37-year-old actress was expecting her son Jack, now 11 months, when she was filming her new movie 'The Witches', and has said she managed to keep her pregnancy a secret on set because her "costume still fit" even with her baby bump.
She said: "I didn't really tell anybody that I was pregnant because I was still in my first trimester. Then, when I went into my second trimester during filming, I only told a couple people. But the costume still fit so I didn't feel the need to tell anybody."
And the star - who has Jack, as well as four-year-old Jonathan, with her husband Adam Shulman - praised the production's costume designer Joanna Johnston as a "legend and genius" for helping her hide her bump, as she had to tell the designer about her pregnancy because she wanted Anne to wear a "corset".
She added to 'Entertainment Tonight': "She was describing the gloves and the gloves having these little nail inserts … and the fabric she was going to use and the silhouettes and everything was just great. [Then she said,] 'I think we should get you, like, a little, you know, corset so you have a wasp waist.' And I just went, 'Oh no, I don't like that one. I don't think so.' And she went, 'What, why?' ...And I couldn't say, 'Because I'm five weeks pregnant.'
"I go, 'I just know myself as a performer and I'm just gonna feel really constrained. I'm gonna feel really constrained and I just, I'm gonna be funnier if I don't have something.' "
Meanwhile, Anne recently opened up on life with two sons, as she said the siblings love to play fight with each other.
When asked how Jonathan is "coping" with having a younger sibling, she said: "No coping, just love. Now Jack's big enough to wrestle with, and that's brought a new element to their relationship that's really cute."