Hi,
For X-Ray we have used metal plate. We didnt know about the pregnancy (Very early stage of pregnancy) but the doctor was very consistence that my wife should use metal plate for the X-Ray(Thanks to God and Doctor). Later we found out that my wife was pregnant.
For medical test, I would recommend you to complete your medical ASAP, the only reason, people(Including me) have faced issue where DMP has failed/delayed the file transfer to CIC. Medical file has to reach to CIC under 60 days.
In my case (Though we were doing our medical well before the expiry date), DMP transferred my and my wife's file to CIC but did not transfer my son's file until 3 weeks for no reason(Doctor has forgot to sign the file).
KvedV.