Are sporting events safe for Pregnant Women?

Patient: Hello Doctor.I have been made aware that while pregnant you should not attend an IMAXmovie theater due to the vibrations caused my the enormous speaker systems. I am planning on taking my 4 month pregnant wife to a professional football game as a surprise. Now I am wondering however if this is safe to do as from personal experience I know that regular crowd reactions can be very intense and seem to cause booming vibrations throughout the stadium. Any advice would be much appreciated. I would hate to put my wife and baby in jeapordy because of a silly game.Thanks, Shilo Zaba