when you get further a long and your doctor grabs where the baby head is to see if your baby is head down, you realize how much "damage" you could really do without it effecting your baby. between that and the pressure for the sonograms. ;)
Our baby has so much protection in there and it should be absolutely fine. If you are really worried and are far along talk to your midwife/doctor/obgyn. I was around 12 weeks when my daughter (5 years old) jumped on me and then again at 14 weeks I had a serious car accident both of which my midwife said I would he fine but just watch for spotting nothing else that really can be done. My baby was born at 38 weeks perfect and healthy
How far along are you? My dog has jump on my belly and everything was ohk. I just try to make sure she doesnt.