The show's 2017 - 'power couple' - who first became friends and allies in the Samoan jungle earlier in the year - couldn't be happier with their pregnancy news.
'It's definitely a big surprise, but we are delighted,' grins 37-year-old Mark, a former Australian Army special operations commander.
'I always knew I wanted to be a father, but I chose not to go down that path. Being a soldier for 16 years, I was lucky to come out intact after so many tours of duty - and to start a family, well that's just a huge deal!'
Diminutive Sam, already sporting a large baby bump 18 weeks into her pregnancy, adds: 'We may not have won on Survivor, but we came away with a much bigger prize. I certainly didn't go on the show expecting to find love. It was not my intention, but I guess it was a really positive thing to come out with.'
On screen, the castaway twosome's chemistry was obvious. Exiting Survivor two days apart - 'I guess I should actually thank the tribe for voting him out,' laughs ultra-marathon runner Sam - they wasted no time getting to know each other better.
'We've been pretty inseparable ever since,' says the 33-year-old mum-to-be, welcoming New Idea into the peaceful country home she shares with Mark in the Dandenong's, near Melbourne.
'He was my number-one alliance, the one I could trust on the show, and then our friendship turned into a more romantic relationship.'
If falling in love was unexpected, pregnancy left the couple flabbergasted.
With Mark away on business she broke the baby bombshell over the phone.
'I can't hide anything from him, so he knew immediately there was something different about my voice,' she says. 'I was going to tell him later, but I couldn't hold back - I did ask if he was sitting down first!'
This article originally appeared on New Idea.