What is the difference between 3D/4D and 2D ultrasound?

2D ultrasound uses high frequency sound waves to produce black and white outlines and flat looking images of the internal organs of your baby. This technology is used at your hospital scan to give you a due date and to look for fetal abnormalities. 3D ultrasound uses the same high frequency sound waves but from different directions so that a 3-dimensional colour image (usually sepia) is produced of the structure’s surface only, usually of your baby’s face. Medically theses 3D images may be helpful in diagnosing issues such as a cleft lip but can also be used for souvenir scanning allowing you to bond with your unborn child at an early stage. With 4D ultrasound, these 3-dimensional images are continuously updated by the machine so it becomes a moving image, just like a movie.