The baby is completely wrapped in blood, bone, and fluid, which keep it well protected.
To your baby, if you sit in a vibrating chair, it's no different than if you were to run up and down the street.
So the massage is usually okay during pregnancy, but not on your hands or feet.
If you get too deep of a massage on either it can cause you to have contractions.
I read this in a pregnancy book.
Make sure to always ask your obgyn before any questionable activity.