A duty of care argument that is predicated on the respondents having not taking action to terminate or suspend the claimants party from undertaking the occupation would take some tortuous argument to not run afoul of laches.
"...ahem, the unicycle rider was unable to ride the unicycle, but wanted to still do so. The rider fell off and hit his head, which would not have occurred had the unicycle owner had stopped the rider from continuing to ride...., thereby the injury was caused by [insert name]"
v
"... did the rider know he was not cut out for riding the unicycle? Was the rider forced or coerced to ride the unicycle against his/her will? Was the unicycle rider given opportunity to sort out his riding skills if the owner knew of the problem?"
If competency was a known issue, then it was known to all parties involved, unless it was a surprise pregnancy... How do you make the elements of the claim without acknowledging that the claimant was aware and thereby has accountability that mitigates the claim, it is essentially a waiver defence.