Pre-employment physical during pregnancy

So I got a tentative job offer for a dream position when I was around 20w pregnant. It's tentative because there's a whole list of requirements to fulfill before the job is really mine. I've been working on them and finally had my pre-employment physical last week (at 26w pregnant) and everything went good...until they tried to send me to a chest x-ray! I had to spill the beans because I couldn't put my baby at risk and I didn't think any x-ray was allowed during pregnancy (despite them telling me they will shield the baby and chest is ok). I convinced them to let me talk to my Ob before getting the x-ray and they let me. I've been going back and reading the fine lines and read that my offer is subject to compliance and passing of my physical! I don't take back my decision to forgo the x-ray but I'm curious if anyone has gone through a similar situation and if they even have grounds to take back the offer because I voluntarily told them about my pregnancy? They should make an exception for 3 months and allow me to wait right? Pregnancy is a contraindication for an x-ray right? I want and need this job so badly! I've worked my a $$ off for it! Why on earth would they even need a chest x-ray to hire me?