Sarah Michelle Gellar went into labour at the gym

Sarah Michelle Gellar was taken by surprise when she went into labour, because her contractions started during a Pilates class.

The Buffy The Vampire Slayer actress gave birth to her first child with husband Freddie Prinze, Jr., a daughter named Charlotte, in September 2009, and she has now revealed the birthing process began during a trip to the gym.

She tells Health magazine, "It was funny, too, because I was getting cranky, and I said to my trainer, 'I'm just cranky today.' She was like, 'Maybe it's because you're going to give birth!' And I was like, 'Nah, not yet.'

"It turned out I was in labour, I didn't realise."