4D Ultrasound Scan – What Is It & How Does It Work?

By (embryologist) and (fertility counselor).
Last Update: 07/17/2014

The 2D ultrasound evolved to the three-dimensional one. Now we have the ultimate advance: the 4D ultrasound or "real-time 3D ultrasound", the newest modality. It integrates the characteristics of the previous ones, but adding other element to the equation: the real-time movement of the foetus, providing a closer look to what is going on inside, the behavior of the foetus and its physiological and motor activity.

Provided below is an index with the 4 points we are going to expand on in this article.


This ultrasound, like its predecessors, is based on ultrasound-emission, and is as harmless for both the mother and foetus as the 2D and 3D are. It is performed using the same scanner as the 3D, adding a specific sounding line.

In order to obtain a good 4D image it is necessary to have a good 3D scan. Therefore, one of the requisites is to have enough amniotic fluid in between the surface to be analyzed and the sounding line. The righ time to undergo such this ultrasound is between the 25th and 32nd weeks, in subsequent weeks the fetal volume increases and the quantity of amniotic fluid decreases, difficulting the obtention of a nice 3D fetal image.

The gynecologist, as well as evaluation the baby, will be able to check the amniotic fluid, the umbilical cord, the placenta, the uterine neck and walls.

Advantages of the 4D ultrasound

One the biggest advantages of this ultrasound is the heart evaluation (cardiac system) and the accurate detection of congenital heart diseases. Thanks to real-time observation, now the slow-time exploration of the heart is feasible, thus making an exhaustive real-time study. All the images are saved in the software, so posterior foetus studies can be made.

The 4D ultrasound present the same advatanges as tthe 3D, but the former has a huge diagnostic value, although many of them are perfomed due to the benefitial psychological impact it has on parents. To see their baby moving inside the uterus gives them more confidence than seeing him/her in 2D.

By way of this technique the parents can see the facial gestures the baby is doing, for instance if the foetus smiles, blinks or yawns. Later, the gynecologist will give them a CD of that unforgetteable moment, so they can keep it forever.

At a diagnostical level, it helps to rule out malformations and genetical pathologies, to analyze the growth of the foetus, to make accurate measurements and assess the condition of different body structures.

Even though tihs ultrasound gives a high-definition image of the foetus, it shouldn't be considered as an actual prenatal diagnosis.

Disadvantages of the 4D ultrasound

  • In advanced gestations, once the pregnancy has reached the thrid trimester, the 3D image of foetus is not as clear as it should be, due to its volume within the uterus and the decrease of the amniotic fluid inside the placenta.
  • It is not always possible to obtain a 3D image, in 10% of the cases a bad fetal position, the placenta, the umbilical cord, the lack of amniotic fluid or even the abdominal fat (obesity) hinders the scanning of a good image.
  • If the exploration time lasts more than 35 minutes,some problems may arise due to the manipulation of the uterus while contracting.
  • Other of the disadvantages of this technique is the the price, depending on the centre, it might be two times the price of a regular 2D ultrasound.

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 Teresa Rubio Asensio
Teresa Rubio Asensio
BSc, MSc
Master's Degree in Medicine and Reproductive Genetics from the Miguel Hernández University of Elche (UHM). Teacher of different Clinical Embryology courses at the UHM. Member and writer of scientific contents at ASEBIR and ASPROIN. Embryologist specializing in Assisted Procreation at UR Virgen de la Vega. More information about Teresa Rubio Asensio
Adapted into english by:
 Sandra Fernández
Sandra Fernández
B.A., M.A.
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

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