I had a HSG in June 07. They put a catheter through the cervix, inject the dye and take x-rays to check the tubes. I took two neurofen beforehand and it didn't do a thing. Mine took an hour to get the catheter through (mostly because of my silly cervix and also because the person doing it wasn't experienced) and was quite uncomfortable and painful and I got a lot of cramping during and after for about an hour or two. BUT thats because I have a stupid cervix that likes to stay shut. Definately take a pad.