'Badass' woman competes in Olympic trials at 18 weeks pregnant

A US athlete has competed in national Olympic trials while 18 weeks pregnant.

Lindsay Flach took on her rivals in one of the toughest events, the heptathalon, while sporting a prominent baby bump.

She announced over the weekend that she had been keeping a "secret".

"The secret is no secret anymore," she wrote on Instagram.

"Every story has an end but in life every end is a new beginning."

Flach, 31, has previously tried out for the 2012 and 2016 Olympics.

The heptathalon sees athletes compete is seven different disciplines: The 800m run, 100m hurdles, high jump, shot put, 200m sprint, javelin throw and long jump.

Flach took part in all seven events, intentionally finishing 100m of the 800m run and eventually placing 15th out of 18 competitors.

The trials took place in the middle of a record-breaking heatwave currently hitting the Pacific Northwest of the United States, seeing temperatures rocket and forcing officials to delay competition until the evening.

Flach's supporters praised her for being a "great role model," a "badass" and a "hero".

"I got emotional and cried watching you compete," wrote one fan on Instagram.

"So happy to see an expecting mother compete at such an elite level! What a story to tell your baby."