I do find the whole "fertility issues" a little hard to swallow.
What I am about to say is from the perspective of someone who suffered recurrent miscarriage (5 in total but 3 losses before we were even referred to recurrent miscarriage clinic) so I'm truly not being facetious.
Having one miscarriage is relatively common (no true stats exist due to women not knowing they are pregnant / chemical pregnancies etc) but it was when I was suffering my losses thought to be 1 in 4 pregnancies end in early miscarriage.
However having one miscarriage does not put you at any higher risk of having another. So one miscarriage - as awful and heartbreaking as it is - is not a fertility issue.
I would never wish a pregnant woman anything but the best. Hope it works out for her / them.