About 3-D and 4-D Ultrasound
  3-D ultrasound can furnish us with a 3 dimensional image of what we are scanning. The transducer takes a series of images, thin slices, of the subject, and the computer processes these images and presents them as a 3 dimensional image. Using computer controls, the operator can obtain views that might not be available using ordinary 2-D ultrasound scan. 3-dimensional ultrasound is quickly moving out of the research and development stages and is now widely employed in a clinical setting. It too, is very much in the News. Faster and more advanced commercial models are coming into the market. The scans requires special probes and software to accumulate and render the images, and the rendering time has been reduced from minutes to fractions of a seconds.
A good 3-D image is often very impressive to the parents. Further 2-D scans may be extracted from 3-D blocks of scanned information. Volumetric measurements are more accurate and both doctors and parents can better appreciate a certain abnormality or the absence of a certain abnormality in a 3-D scan than a 2-D one and there is the possibility of increasing psychological bonding between the parents and the baby.
 An increasing volume of literature is accumulating on the usefulness of 3-D scans and the diagnosis of congenital anomalies could receive revived attention. Present evidence has already suggested that smaller defects such as spina bifida, cleft lips/palate, and polydactyl may be more lucidly demonstrated. Other more subtle features such as low-set ears, facial dysmorphia or clubbing of feet can be better assessed, leading to more effective diagnosis of chromosomal abnormalities. The study of fetal cardiac malformations is also receiving attention. The ability to obtain a good 3-D picture is nevertheless still very much dependent on operator skill, the amount of liquor (amniotic fluid) around the fetus, its position and the degree of maternal obesity, so that a good image is not always readily obtainable.
 More recently, 4-D or dynamic 3-D scanners are in the market and the attraction of being able to look at the face and movements of your baby before birth was also enthusiastically reported in parenting and health magazines. This is thought to have an important catalytic effect for mothers to bond to their babies before birth. What are known as 're-assurance scans' and the rather misnamed 'entertainment scans' have quickly become popular.
Most experts do not consider that 3-D and 4-D ultrasound will be a mandatory evolution of our conventional 2-D scans, rather it is an additional piece of tool like doppler ultrasound. Most diagnosis will still be made with the 2-D scans. 3-D ultrasound appears to have great potential in research and in the study of fetal embryology. Whether 3-D ultrasound will provide unique information or merely supplemental information to the conventional 2-D scans will remain to be seen