A 4D scan is as safe as the conventional 2D scan. Ultrasound scans, unlike X-rays or CT scan, do not employ any form of radiation.
The only theoretical risk is that of raised temperature. It is a well known scientific fact that the sound waves do cause a rise of temperature in the tissues where they pass through. The rise in temperature is dependent on acoustic power and scan duration. All modern scanners display what is known as a Thermal Index (TI). The index tells the operator about any change in tissue temperature. It is displayed continuously on the screen and therefore the operator stays within the accepted safe Thermal Index range.
There is solid evidence that elevation of temperature by 1.5°C above normal (37°C) is perfectly safe. In practice, this is rarely reached. It is also true that, in theory, the tissue temperature needs to rise to about 41°C to have the potential of causing harm. It is virtually impossible to reach this temperature in regular pregnancy ultrasound scanning
The paragraph below summarises the recommendations of the British Medical Ultrasound Society (BMUS) with regard to social scanning.
“Very little information is currently available regarding possible subtle biological effects of diagnostic levels of ultrasound on the developing human embryo or fetus, and the possibility of developmental effects in the brain cannot be ruled out. There is evidence that diagnostic levels of ultrasound can influence development of the brain in small animals, although it is not possible to extrapolate this finding to the human situation. A balance must always be maintained between diagnostic benefit and risk to the patient.”
In order to limit any possible effect of ultrasound on the developing embryo/fetus, all times stated are approximate and scanning duration will be conducted on an ‘as long as required’ basis to provide the relevant information.