Yes, it's bad. Can't remember the stats, I heard Rhea Dempsey talk back in September I think, and a normal and natural (NO intervention whatsoever, drugs etc, includes things like stretch and sweeps...and even internals I think (?) although that could be wrong, I'll find my notes from that night and come back) is very rare. Will be interested in this thread
Having an internal does not interfere with the mechanism of birth, so having one does not mean you did not have a natural birth. However it may lead to a suggestion of an intervention, which would mean birth being no longer fully natural.