The lethal outside back has already achieved more than most 23-year-olds, and she can now add playing in a rugby league World Cup to that list after featuring in Australia's thumping 38-0 win over England on Sunday.

Yet her finest achievement is six-year-old son Carter, already a junior rugby league player with the Cronulla-Caringbah Sharks.

McGregor fell pregnant while she was still attending Woolooware High School, across the road from Southern Cross Group Stadium which is hosting the World Cup, and had to forego her remaining secondary school studies.

"When I first found out, obviously it was a bit of a shock but I saw the positive in it straight away and he's a blessing to me now, I wouldn't have it any other way," McGregor said.

"I was year 11 when I had him so I didn't get to finish year 12. It's not what all year 11 [students] do. It was pretty crazy, I'm just really lucky I had really supportive parents and partner at the time.

"I was so young and they knew the talent that I had and they didn't want me to waste it. I was really lucky that I still had them supporting me and encouraging me to go as far as I can in my sporting career."

At the time McGregor's talent was manifesting on the netball court, and on Oztag and touch football fields.

It wasn't until fellow Jillaroo Maddie Studdon suggested McGregor give rugby league a try that she laced up the boots for the first time.

That was in 2014, a year after the Jillaroos beat New Zealand in the last World Cup final. McGregor started off playing for the Helensburgh Tiger Lillies before making her NSW debut a year later.

Twelve months ago she became just the second woman to sign a playing contract with an NRL club, joining Australian enforcer Ruan Sims at her beloved Cronulla Sharks.

Earlier that year McGregor made her Australian debut at the Auckland Nines, and she played her first 13-a-side international Test against New Zealand in May.

After her belated introduction to the sport, she has become one of the most dangerous backline players in the women's game.

"I have four brothers, it's in my nature to be on the footy field, I loved watching it with my Dad and my brothers," McGregor said.

"I had my first game with Helensburgh. From there I was just lucky enough to get picked into different teams and here I am now, my first World Cup which is pretty crazy after only three years, it's been a dream come true.

McGregor will play at fullback on Wednesday against Canada with livewire Nakia Davis-Welsh to be given a rest after featuring in the opening two pool games.

Regular No.1 Sam Bremner will miss out again as she's nursed back from a pre-existing leg injury, but she's still expected to feature in the finals.

Sims will captain with Steph Hancock getting a spell. Renae Kunst is set to play despite a cramping calf late in the win over England on Sunday.