A 2D ultrasound transmits the traditional black & white ultrasound pictures. These pictures show two-dimensional outlines and profiles of the baby. This specific ultrasound is often used to listen to the heartbeat of the fetus and determine gender.
A 3D ultrasound captures three-dimensional images of your baby. The transducer (sound wave transmitter) sends out sound waves from numerous directions and as a result, transmits realistic three-dimensional still shot images.
A 4D ultrasound utilizes the same technology as 3D ultrasounds but introduces the element of motion. This technology allows you to take a look in the womb to see the movement of the fetus. If your baby is feeling like giving you a show, you may be able to see things like your baby yawning, smiling or sucking its thumb!