Kate Hudson ''panicked'' when she had her head shaved.

The 38-year-old actress got a buzz cut for a new project with Sia and admits she suddenly had a huge panic about the shape of her head now her hair wasn't covering it and likened the big reveal to finding out the gender of a baby when its born.

Speaking on Jimmy Kimmel Live, she said: ''It's funny, too, because when [the cut] first started, I didn't think about it because it was for the role. It was like, 'Oh, let's do this!'

''I didn't think about it until it started. Oh! What is the shape of my head going to look like? I really started to panic. And all of the sudden it was like a birthing, like, 'It's a boy!' But 'It's round!'''

Meanwhile, Kate previously revealed she loves the ease of having a shaved head compared to her long blonde locks.

She said: ''I like the ease of it, you know what I mean? When I looked at the hair when it came off I was like you know this is...I'm so happy this is gone. It was a lot of wear and tear on that.''

However, the 'Marshall' star admitted her 13-year-old son Ryder - who she has with ex-husband Chris Robinson - wasn't so keen when she first had her head shaved because it was similar to his own hair style.

Kate - who also has six-year-old son Bingham with her ex Matt Bellamy - added: ''I copied Ryder. Ryder had it way before, Ryder's been buzzing his head for a long time. Ryder's like, 'Mom, you're cramping my style.' But when I did it, he was like, 'Oh my God, we actually ...' It was the first time he even could see that we looked, you know, that he looked like his mommy. Now it's starting to grow out, and Ryder's growing his out.''