I hope this makes sense...
So I presume if you were in the very, very early days of a pregnancy and you thought you were having a MC (like a 'chemical pregnancy') you wouldn't bother going to the doctor, because what could they really do or tell you? You'd just keep testing maybe and see if the line fades or gets darker?
But at how many weeks gestation would it be worth going to the EPU for a scan if you started bleeding?