Though traditional ultrasounds—like the —can be a great tool, medical communities from around the globe, including and , have expressed concern over the safety of 3D and 4D ultrasounds, in particular.
And that means you would have to be ultrasounding the exact same peice of tissue on the fetus for days before any real damage to happen.
As you can see in the picture below, 2D and 3D ultrasounds produce dramatically different images.