You can choose to the do the medicals without the xray the panel physician will send the results with a note to the IRCC about the XRAY (which will be done later). If you decide to do the Xray, at 2nd trimester it is safe, the panel physician will advice you more about this, and during the xray they put a double or triple shield to protect the baby. Its also a good idea to talk to your own doctor before going, check that everything is okay with the baby (the one that you have been seeing during the pregnancy)