A British woman who ran the London Marathon to break a world record for the fastest marathon time for a woman wearing a nurse's uniform was told her attempt did not count, because she wore her scrubs.

Jessica Anderson, a nurse at Royal London Hospital, finished last week's marathon in a time of 3.08:22, half a minute faster than the existing marathon record for a woman in a nurse's uniform.

But she was told by Guinness World Records beforehand her race attire of medical scrubs with trousers didn't meet Guinness's rules for a nurse's uniform: a blue or white dress, apron, and a traditional cap.

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"I was quite taken aback when I read that they’d rejected my application and I did email them to ask them to reconsider but they said no. I get that it’s supposed to be a fun thing but their definition is just so outdated," she told Runner's World magazine. "Some of the nurses I work with do wear dresses but mostly we wear scrubs or a tunic and trousers. I’ve certainly never seen a male nurse wearing a dress to work."

Anderson said she knew about Guinness' rules before the race, but that didn't deter her from trying to reach her goal.

"Guinness world records have declined my application as my uniform doesn’t meet their criteria of what a nurses uniform should be but I will still be aiming to beat the current official record time of 3hrs 8 minutes 54 seconds," she posted to Instagram in March.

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Guinness World Records said on Saturday that it would review the garment policy going forward.

"Inclusiveness and respect are values that Guinness World Records holds extremely dear and while we always need to ensure we can differentiate between categories, it is quite clear that this record title and associated guidelines is long overdue a review which we will conduct as a priority in the coming days," the group said in a statement.

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Anderson, who raised more than $3,000 for Barts Charity, told Runner's World she just hopes the group looks at policy going forward.

"I’m sure Guinness World Records don’t intend to cause offense, but it would be nice if they decided to revise their criteria instead of reinforcing old gender stereotypes," she told the magazine.

Last Sunday marked the 39th running of the London Marathon, which saw over 42,000 people cross the finish line.

The Associated Press contributed to this report.