It probably depends on the reason for the procedure. If the doctor is trying to diagnose why you have periods that are unusual in some way, it probably doesn't matter. If the doctor is trying to look at a polyp, it might be worth calling in to find out if it matters. (I'd be surprised that if there was sensitivity to the issue of whether you have a period or not, they wouldn't tell you to come in on a certain day or even put you on the Pill to make you have a certain kind of lining.) But call and ask.