...Congartulations in advance!
Do NOT Worry !! go ahead and do all the required medical tests, don't delay your process!
Any MD knowing that she is pregnant, will take ALL the necessary precautions to protect her and the baby...they're in the medical field for a reason...ethically, they can not puposely cause any harm to a patient, and that of course include unborn children. When she goes for her exams she should immediately let the doctor know that she is pregnant, maybe, if possible, bring confirmation of the pregnancy from her OB-GYN to help determine how far along she is, and they will take it from there.
The message I posted earlier today was copy-pasted from IMM-5419, Appendix VII, Section E, of the "Designated Medical Practitioner Handbook".....and it reads:
...."OF the examinee is pregnant, the film must be full sized, the field size must be strictly limited and there must be abdominal shileding"....
I understand your concern for your wife and your baby, but don't be afraid, the doctors will know what to do considering her situation. Even if your wife forgets to mention it, an X-ray technician before performing any X-rays should ask a woman if there are any chances that she could be pregnant. They are required to ask that safety question, and it's funny that they even ask this to women in their 50's and 60's (just in case!). I'm also getting this info from my wiffe, she sees this things all the time, as she works at a local hospital in the Maternity Ward.