Abnormal Pap?

At my first appointment with this pregnancy at 12 weeks, I was given a Pap smear. I have yearly appointments, never had a problem. Now I go back next week at 16 weeks for a colposcopy. The woman who called and told me the appointment needed to be made was so vague and didn't really tell me what to expect. I'm not freaking out but I am a bit nervous. I called and spoke with my doctors nurse and she implied it may be just because of pregnancy and a weakned immune system. Anyone have a similar experience? Almost everything I've read online points towards this being a pre-cancer check.