George North will have to consider his future in rugby union if he suffers another concussion, according to former World Rugby medical adviser Dr Barry O'Driscoll.
Wing North took an extended break from rugby in 2015 after sustaining a number of head injuries while playing for Northampton Saints and Wales.
The 23-year-old returned to international action at the Rugby World Cup as Wales reached the quarter-finals, and has been key in their unbeaten start to the Six Nations.
With growing concern over head injuries in the sport, Dr O'Driscoll believes North would have to put serious thought into his future in the sport should he suffer another concussion.
"I'm sure if [North] gets another one he will have to consider whether the worries about what the inference is from these is enough to make him give up the game," he told BBC Sport.
"It's his living and it's a very good living and he loves it ... and he would I'm sure and his advisers would make him think seriously about it.
"But it's a balance for each person to make and I don't think we're anywhere near the stage of the game of saying 'no, that's it, we can't pick you anymore', [because] we don't know enough yet.
"But any player at all who has had three or four concussions, in my opinion must seriously think about the future."