Definition & Overview

A 3D ultrasound, more technically known as phased array ultrasonics, is a medical sonography technique patented in 1987. While also useful for medical evaluation and diagnosis, it is most commonly used for obstetric purposes, specifically for capturing three-dimensional images of a foetus during pregnancy.

During a sonography scan, high-frequency sound waves are sent inside the body. The sonogram machine then sends them back at different angles creating echoes that are translated into three-dimensional images.

Who Should Undergo and Expected Results

3D ultrasound is often recommended for those who wish to have clearer images of their unborn foetus in comparison with the results provided by a conventional 2D scan. The procedure is best performed between the 24th and 32nd weeks of pregnancy. Beyond the 32nd week, the foetus begins to descend into the pelvis, making it more challenging to get good 3D images.

The scan is also helpful for patients who wish to determine the gender of their unborn child. For this purpose, the scan is usually performed between the 16th and 20th week, during which the accuracy rating is at 99%. It is important to note that the use of 3D ultrasonography to have a clear visualisation of the unborn foetus and to determine the gender during pregnancy, although very common, is purely elective.

Reasons for performing an ultrasound scan may differ depending on the stage of the pregnancy. During the first trimester, most scans are performed to:

  • Examine the placenta, uterus, cervix, and ovaries
  • Look for abnormalities or abnormal growths in the foetus
    During the second trimester, most scans are performed to:

  • Determine the baby’s gender

  • Check for placenta previa or placental abruption
  • Check for congenital and structural abnormalities, and problems with blood flow
  • Check for pregnancy tumours
  • Examine suspected foetal anomalies, like spinal cord problems or cleft lip palate
    3D ultrasound scans are deemed more effective than a 2D scan in detecting or confirming suspected problems during pregnancy since they are able to provide more detailed images. However, like 4D scans, they are not considered as part of routine prenatal testing. 3D scans are only capable of producing still images, whereas 4D scans, which incorporate time as the 4th dimension, can produce moving videos of the foetus in utero.

How is the Procedure Performed?

During a 3D ultrasound, the patient is asked to lie down on an exam table. The obstetrician or ultrasound technician will then apply a gel-like substance to the patient’s belly. A transducer probe or wand is then placed against the belly and moved around to get the best images possible.

The procedure can be performed in 10-15 minutes, depending on the position of the foetus. It is entirely painless and the pregnant mother is generally comfortable all throughout.

At the end of the scan, the patient may opt to take home copies of the 3D foetal images produced during the scan.

Possible Risks and Complications

3D ultrasound scans are guaranteed safe and harmless for pregnant women and their unborn children. The FDA limits the amount of energy used during the procedure to just 94 mW/cm2 and most 3D ultrasound machines manufactured for the sole purpose of obstetrical ultrasound scans often have their energy level set below FDA limits.

Nevertheless, a number of medical organisations still recommend that parents be made aware of the possible risks of ultrasound energy exposure during the scan. Once ultrasound energy enters the body, it can generate heat in the tissues and may also create gas pockets in the tissues and body fluids.

Due to such claims, several studies have been conducted to assess the risks that come with 3D ultrasound. Some showed a correlation between the use of ultrasound and left-handedness in male babies, which is considered a sign of brain problems except in cases where it is hereditary. There is also a link between ultrasound and various neurodevelopmental problems that commonly affect children such as speech delays, dyslexia, mental retardation, and schizophrenia, among others. Additionally, a 2006 study performed on pregnant mice showed that ultrasound exposure caused brain damage that is consistent in nature with that detected in the brains of people suffering from autism. These negative effects, blamed primarily on tissue manipulation, however, are linked to long-term exposure to ultrasound energy. Since ultrasound scans are performed in a short amount of time, the risk involved is minimal.


  • Fenster A., Downey DB., Cardinal HN. (2001). “Three-dimensional ultrasound imaging.” Phys Med Biol. 2001 May;46(5):R67-99.

  • “Ultrasound Imaging.” US Food and Drug Administration.

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