Go and find another find another dentist!

I used to be a Dental Nurse and we would pull teeth of pg women. Local anaesthetics are fine during pg. If the tooth is that bad, it will get infected, which will mean a course of antibiotics for you. Did your dentist forget to mention that effective root canal therapy also requires an X-ray along the way? (to see if all the root has been removed). If he is your regular dentist, then he should already have some X-rays and should be able tell the root position from that (if that is what he wanted to x-ray for).