3D -4D differences?

Question

my doctors office had 3D ultrasound when i was pregnant with my son 2 1/2 years ago now they offer 4D. what's the difference??

Answer

I'm doing 5D this time

Answer

This is from the sheet of paper my obgyn gave me about the differences. I honestly couldn’t tell a difference in 3D vs 4D when I did a google image search. 
3D:
3D technology utilizes the same high frequency sound waves as 2D and is just as safe to use. The sound waves create reflections from different angles to each other; the ultrasound machine then integrates these reflections with its high-speed computing software
4D: 
It is 3D with the addition of real time. Meaning while the ultrasound is being performed and you are watching your baby LIVE, the real time is considered the 4th dimension

3D -4D differences?

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