Does anyone know the reason it says “pregnant women should not use this machine” on the message chairs at the mall?

They can cause contractions I think. I used them at nail salons my entire pregnancy, not as intense as the mall ones though. They just don't want to be held liable.

It can cause contractions if you’re on to long

I tried them once with my second child and it made my body hurt so bad I felt like I was dying lol there are massages that pregnant women can get just make sure the person is specialized in pregnancy massages