For example, 3D fetal ultrasounds bombard a baby but they are really only done out of pure vanity for parents. They don't tell doctor's anything they don't already know from the boring standard ultrasound.
Doesn't really seem that way. The FDA has issued a statement on fetal ultrasound imaging: http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm095508.ht...
The crux of it is:
The long-term effects of tissue heating and cavitation are not known. Therefore, ultrasound scans should be done only when there is a medical need, based on a prescription, and performed by appropriately-trained operators.
And I too would have never have thought about fetal ultrasounds being unsafe, had it not been for your post.
I was having chronic muscle spasms in my right shoulder blade area, and the physical therapist used therapeutic ultrasound on me. It melted the spasms like butter. Several months of terrible pain gone in an instant. I was never so tempted to steal a machine in my life.
Good presentation: http://radiology.ucsd.edu/body_image/pdfs/visitors/bohazards...