Ultrasound is the only radiological imaging modality that is completely safe to use during pregnancy. Other modalities such as X-rays and CT Scans use ionizing radiation that can alter the normal physiology in our body's cells. As it can have an effect on cell division, it should be avoided before 12 weeks and only used in extreme cases under the guidance of your radiographer after 12 weeks.
Ultrasound is sound waves outside the human audible range. The transmitter reads the speed and time of pulses returning from the tissue in the womb. This information can be interpreted by the software of the ultrasound machine. This image is used to give us important diagnostic information and 3D images and 4D video clips that could show you a clear image of your baby.
3D Ultrasound is a medical ultrasound technique, often used during pregnancy, providing three-dimensional images of your fetus.
4D Ultrasound is similar to 3D ultrasound images except that movements can be viewed and recorded!
Below are pictures gathered from different scanning sources: