It seems like it is possible with some elevations, itself the DMP manual says this. Found some interesting comments n links go through with them.
" I have done my Medical on 14th of Nov
My wife is 24 week pregnant....
IOM offer us 3 different options regarding my wife pregnancy
1. we can do X-rays with protective shield now
2. we can do all the tests apart from X-ray which can done after delivery or
3. last month of pregnancy (which is totally safe as they told us).
we have chosen 2nd option
they gave us a letter that i have to send CHC London and they kept photo copy of that letter and they will send that photo copy to India but they will not send my wife's other test reports (blood and urine) to CHC, they will keep those reports and will send altogether later with X-rays after the delivery.
hope it will clear you all the points at this stage '
http://www.canadavisa.com/canada-immigration-discussion-board/pregnancy-and-medical-exam-t125043.0.html
http://www.cic.gc.ca/english/department/partner/pp/pdf/IMM5733E.pdf