Williamson said she was concerned about it flaring up before England's semi-final against Sweden, which they went on to win 4-0.

"I was like, 'it cannot happen'. I actually won't be able to play," Williamson said.

Endometriosis occurs when tissue similar to the lining of the womb grows elsewhere.

In an interview with Women's Health magazine

she added: "Before the Euros I had a concussion, which they say can really impact your next period, and it was bad.

"You know when you're on the bathroom floor and literally like: 'I can't move.' When it's too late to take the tablets because I'm, like, in it now."

She added that having an endometriosis flare-up "is a big fear when you get to a tournament not injured".

When asked how she has dealt with the difficult periods that characterise the condition, the Arsenal defender said: "I'm a professional athlete, I've always been like, 'let's get on with it'.

"But you get to a certain age when you actually say: 'this is a really big problem'. I'm pretty sure if men had periods we would have figured out a way to stop them by now without doing any damage."