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. 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.
3D ultrasound was first developed by Olaf von Ramm and Stephen Smith at Duke University in 1987.
Clinical use of this technology is an area of intense research activity especially in fetal anomaly scanning but there are also popular uses that have been shown to improve fetal-maternal bonding. 4D baby scans are similar to 3D scans except that they show fetal movement as shown in the video clip.
If the system is used only in the Obstetrics Application, the ultrasound energy is limited by the manufacturer below FDA limits for obstetrical ultrasound, whether scanning 2, 3 or 4 dimensionally. (The FDA limit for obstetrical ultrasound is 94 mW/cm2.) While there is no hard evidence for harmful effects of 3D/4D ultrasound, its use in non-medical situations should be undertaken with the understanding that a risk may exist.