Like regular ultrasounds, 3D and 4D ultrasounds use sound waves to create an image of your baby in your womb.

Using 4D ultrasound, a new research shows the effects of smoking on the movements of the tiny faces of unborn babies.

A team of researchers from Durham University, UK, has been analyzing data from 4D ultrasound scans which create three dimensional renderings of unborn children that depict motion in real time.