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2D - 3D - 4D baby ultrasound scans

What's the difference?


In a sentence (or two!) a 2D baby ultrasound scans show flat cross-section images of your baby, 3D baby ultrasound scans use these slices to show still images of your baby in three dimensions and 4D baby ultrasound scans use these 3D images to show live movement of your baby in three dimensions, with time being the fourth dimension. 


Although this explanation seems pretty straightforward the best way to understand this is to visualise this - so if you imagine a cube (maybe even a toy building block which is a cube!) and let's say you cut this in half, placed it on a table and look directly at it face on - you would see something like this:


This is a 2D representation of what you would most likely see as you are looking at it face on and represents one "slice" of the cube where it was cut in two. Now say you cut the cube into 10 slices for example - and did the same thing of placing them down and looking straight on then the slices would be looking at different cross-sections of the cube. Similarly 2D baby ultrasound scans use ultrasound waves to look at different "slices" of your baby to look at internal organs and other anatomical features/landmarks (depending on the stage of the pregnancy and which scan is being performed).


Let's take this further and say your friend comes along and says "I like all these slices, but what did your cube block look like before you cut it into pieces!" in order to show your friend what you could do is get all the ten pieces and put them back together and you may seem something like this:


This now looks like the cube block you started with and doesn't show any cross -section but the shape and surface of the cube as a whole - so essentially you have put all the slices together like a jigsaw puzzle to get the original shape and surface of the object. This is very similar to how a 3D baby ultrasound scan works, the 2D images are "put together" by the ultrasound machine to show your baby as a whole and the surface shape of your baby which allows you to not see cross-sections (a 3D scan can be used to do this but this is not routinely done and is more specialised where there is a medical need) and but surface features like lips, nose, hands, etc. (depending on the stage of the pregnancy).


Now I know what you must be thinking - how can you take this into 4 dimensions! well as we started off by saying the fourth dimension is time so if we go back to our cube block analogy, lets say you and your friend are very happy as you now understand the difference between 2D and 3D ultrasound scans and you get a call from another friend who is not able to see the block in front of you and really wants to see what the block looks like from all sides - you could take a few pictures on your phone and send to your friend or you could take a video and move the cube around in your hand to show each side and send that - which may look something like the below;



As you can see the video is showing the cube blocks different sides and can be said to essentially be made of 3D images joined together as we are still only looking at the surface of the shape. This is what a 4D baby ultrasound scan is the ultrasound machine takes multiple 3D images of different sides/angles of your baby and joins them together to get a live moving image - the real excitement of 3D and 4D baby ultrasound scans are that you can see your baby's features and see your baby moving in real time as the ultrasound machine is constantly taking images in 2D to build up the 3D image to join together to a 4D moving image/ clip so if you see your baby yawn or kick or stick he/her tongue out then that is happening at that moment.




3D and 4D scans are considered as safe as 2D scans, because the images are made up using 2D scan images and ultrasound in general is considered the only imaging technique to be safe to use with pregnancy due to the lack of ionizing radiation however we always recommend discussing any additional or private scans with your midwife or your health care professional look after your maternity. 


There’s no evidence to suggest that the scans aren’t safe, and actually studies have shown these scans help encourage bonding between mother and baby as you get to see your baby prior to birth. All of our 3D - 4D ultrasound scans are performed by trained experts.


Currently there is not widespread use of 3D - 4D baby ultrasound scans in the diagnosis of any conditions, etc. hence this type of scan is not routinely available on the NHS but is able to be booked with us at any of our clinics where our machines are connected to nice large screens where you can share the experience with family and loved ones.


4D Baby Scan (22).jpg




The scan clinic offer the scan between 22 to 32 weeks pregnant and recommend the best time to have a 3D or 4D baby ultrasound scan is when you're between 24 weeks and 28 weeks pregnant. Before 22 weeks your baby has very little fat under his/her skin, so the bones of her face will show through. After 32 weeks, your baby's head may go deep down in your pelvis, so you may not be able to see his/her face.


It's natural that you'd like to see your baby's face on the scan. But sometimes it's not possible, and the quality of the images are dependent on factors such as fetal position, gestational age, mothers BMI, scar tissue and amniotic fluid, which are constantly changing from day to day and are beyond the control of The Scan Clinic and its practitioners. If your baby is lying facing outwards, with a good pool of amniotic fluid around her features, you should be able to see the face. But if your baby is facing your back, his/her head's far down in your pelvis, or there's not much fluid around, you won't see much. The same applies if you have a lot of tummy fat.


We will always endeavour to obtain the best results on the day and may ask you go for a walk, drink some water and some other tips and tricks we have up our sleeves however If adequate image(s) of your baby cannot be obtained due to such circumstances we may substitute your scan for an equivalent 2D scan OR you can choose to book a 20 minute re-scan at a discounted price. Further information can be found on our 3D 4D baby bonding ultrasound scan page which you can get to by clicking on the button below.


Click here to check out our 3D - 4D Baby Bonding Scan




1. BabyCentre