[Figure 1: 2D Ultrasound]	[Figure 2: 3D Ultrasound]

3D ultrasound is a medical ultrasound technique used during pregnancy, providing three dimensional images of the fetus. Often these images are captured rapidly and animated to produce a "4D ultrasound".

There are several different scanning modes in medical and obstetric ultrasound. The standard common obstetric diagnostic mode is 2D scanning
[Figure 1]. In 3D fetal scanning, however, instead of the sound waves being sent straight down and reflected back, they are sent at different angles. The returning echoes are processed by a sophisticated computer program resulting in a reconstructed three dimensional volume image of fetus's surface or internal organs; allowing one to see width, height and depth of images in much the same way as 3D movies but no movement is shown.