My Papsmear came back SLIGHTLY ABNORMAL, is this Okay or Not?

I'm close to 18 weeks pregnant and I had my Doctor visit 3 days ago. The Doctor told me My Papsmear came back SLIGHTLY ABNORMAL. and that in a few weeks he will Check me again with a Microscope to see what It is. Is this Normal & will it Harm my Unborn baby? He said it was SLIGHTLY, so I don't see why he has to Check me again. & How in the World is he going to Check with a Microscope? This is My First pregnancy, so I'm kind of Scared.