Urgent! Help!

I am applying for immigration to Canada and my interview date is in the next month. But now I get a problem. I am pregant for two months and worried about the physical examination. Since I was told every one was required to go throght X-ray, which would hurt my baby. I am wondering if anyone knows that in my situation, can I ask the Canada Immigration office to postpone my physical examination date or should I ask to put off my interview date? Anyway, what proper things I should do? Please give me suggestions. I am in my thirties and really expect the baby. Thank you very much.