Turia Pitt found out she was pregnant three days before she was due to leave Australia to climb to Mount Everest Base Camp.
The 29-year-old burns victim turned motivational speaker has told 60 Minutes on Sunday night she is 15-weeks into her pregnancy and due to give birth in December.
She says she told partner Michael Hoskin while he was brushing his teeth.
"I just walked in and I left the pregnancy stick there," Ms Pitt said.
"It makes me really stoked that I'm still here and I get to experience this."
She told 60 Minutes she knows Hoskin will be "an amazing dad" because of how he has cared for her since she was badly burnt when a bushfire ripped through the track while she was competing in an ultramarathon.
"He had to look after me for years, and he was so patient, so caring," she said. "I think those qualities, especially in a parent, are really desirable."
Ms Pitt and several other competitors suffered burns covering more than 60 per cent of their bodies while running in the 100km race in WA's Kimberley region in September 2011.
She has gone on to become a motivational speaker and fundraiser for reconstructive surgery charity, Interplast.
Despite the injuries she sustained in the fire – all external – Pitt told 60 Minutes she is confident she will have no trouble carrying or delivering the baby.
"We've been through something pretty traumatic, and we're past that stage now," Hoskin said. "I reckon this will be more fun."
Fairfax Media with AAP