I doubt very much that it matters, but I remember some people worrying in a thread some time ago about a gravid snake that was x-rayed. I think a safer option is always going to be ultrasound, as x-rays can be potentially damaging to developing embryos (which is why pregnant woman aren't x-rayed). Just something to think about I suppose; like I said, I'd be surprised if you had any problems. Good luck with the clutch!

Cheers,
-Matt