"I went on some amazing digs as a student and it was all very romantic and inspiring," Ms Yeaman told news.com.au.
"We did some magical digs in the Kimberley at 50,000-year-old sites, which was mind-blowing and I loved it.
"I literally did one paid contract job so I'd be embarrassed to call myself an archaeologist, but I finished my honours degree and after a week I found out I was pregnant, so it was a very short-lived career."
Ms Yeaman found herself at home "doing nothing" and also soon realised that even after her baby arrived, she wouldn't have been able to afford a nanny when she was away at sites, so she decided it was time to give up her dream career – a decision that left her feeling "thwarted".
Desperate to find her next career move, Ms Yeaman began reading business books and writing up business plans after focusing her "mental energy" on entrepreneurship.
At the same time, she had struck up a friendship with another mum-to-be, Roma Burke, in their obstetrician's waiting room over several months.
Ms Burke was working in hospitality at the time but was also planning on a career hiatus after her baby arrived, and eventually the pair decided to go into business together.
They spent a year "talking about babies" and also devising a methodical business plan, and their first venture, That's Mine – an online store that sells stick-on labels – launched in late 2001.
But the business partners ended up having two children each – and when their young kids reached the "dressing-up phase", the mums realised they were sitting on another lucrative opportunity.
They considered adding kids' costumes to their business offering, but a "chance meeting" with someone who sold animal dress-ups convinced them to look into the industry more closely, and they ended up flying to the US for the New York Toy Fair.
The duo realised the potential and originally planed to only sell kids' costumes but were told that would be a "mistake" as 70 per cent of the US and European costume market was targeted at adults.
And within a few hours of launching their online costume store CostumeBox in late 2007, the first order came through – an adult "naughty nurse" costume.
"We knew right then that's the way it was going to be. Before we launched we changed our name from kidscostumes.com.au to CostumeBox and it was very fortuitous," she said.
"We weren't expecting it to be a hit – we thought we might get to $103,000 turnover in a year.
"But we turned over a million which was a surprise to us, but I think it was because we were one of the few broad, family-friendly online costume stores that existed then."
She said it was a "fun but scary" time as the business grew and admitted to having a few "white-knuckle years" as they balanced the business expansion while struggling to keep up cash flow.
"There were a lot of mistakes and wobbly moments, like when the exchange rate moves against you, or when a shipment arrives after Halloween instead of before, or when a container of Santa costumes falls off a ship and ends up covered in seaweed," she said.
But the hard work has now well and truly paid off.
CostumeBox, which sells a huge range of dress-up outfits, costume accessories, party supplies, gifts, novelties, collector's items and craft materials, now operates out of a sprawling Sydney warehouse.
It sold 140,000 costumes last year alone and has evolved into a $20 million business that's set to grow by 25 per cent this year.
Despite that initial sad career setback, Ms Yeaman is adamant she has no regrets.
"I regret nothing because it all led me to this point, and I don't think I would have become an entrepreneur if I'd studied business instead of archaeology. I probably would have
ended up working for a big corporate," she said.
