I would not be hurt at all. They are hardly likely to have planned it to be on that exact day after all!
I would congratulate them.
I keep bearing this one in mind, Been TTC for 5 years unsuccessfully for #2. My sister gets married next June in Las Vegas. My 7y DD is bridesmaid. We have flights and hotel booked. But should I be actively doing something to ensure I don't fall pregnant in this time (think the next 3 months are the problem months with regrds travelling now). TBH I have done nothing. If it happens, it happens. I am sure mys ister would be just happy for me and DH to have finally achieved the pregnancy. My DD, however, would probably be rather upset at not being able to go!