SIL said the same thing about her pregnancy! IBS before, then could eat whatever she wanted while pregnant, then IBS came back not long after she gave birth.

I also had IBS for quite a few years, and one thing I did find helped was to not have fluids with main meals. I don't know why it worked, but it did!! My grandparents always refused to give us drinks with our meals, maybe they were onto something! (or maybe it was a mind over matter thing for me)