first of all what is the difference between a 3D scan and a 4D scan?
secondly, how do i go about getting one for my pregnancy. i am currently 21 weeks and live in brisbane and am doing shared care at the Royal Brisbane hospital.

i have heard you have to pay for them, but a friend of mine got a 34 week scan at the public hospital to check on her placenta previa and the print outs they gave her were in black and white but looked like 3D images and it was free.