Hi My girl had her baby at day 65 but to be honest she did find him hard to pass and i had to help push his head out and he was already out of his sack and was dead
so lucky i managed to get him breathing again.
I would say take her to the vets as i have heard that after day 67 cats can find it hard to pass the kittens through the birth canal, plus the plazenta doesnt last long after that before it starts to go bad.
But i am sure there are plenty of other breeders on here that may have some other advice on what they have experenced after day 67.
But good luck and please keep us updated
xx