3D and 4D ultrasound are actually safe for the fetus. However, when you do an ultrasound, the fetus is also exposed to sound waves for a long time. The ultrasound examination can take up to 45 minutes, and this is beyond the recommended safe limits. If you want to monitor fetal development, 2D ultrasound is actually enough to answer that desire. The resulting image contains all the information you need, including physical and organ abnormalities. 3D and 4D ultrasound do provide more thorough and realistic results. However, they are more suitable for detecting health problems that are not seen on 2D ultrasound. Whatever type of ultrasound you choose, make sure you have consulted with your obstetrician.