Ultrasound works just like radar to make pictures of the internal organs or baby, except it uses very weak sound waves.  Because they are so weak they can do no damage and that is why they are used to look at babies.
Doppler Ultrasound
A Doppler study uses ultrasound to measure how fast the blood is moving through your arteries and veins. It can be used to measure how much blood a baby is getting and also to diagnose blood clots, heart problems and blocked or narrowed arteries.
What to expect?
Most scans are done lying down and don't hurt. The pictures are made by moving a small camera over your bare skin. We use a small amount of contact jelly to help the sound waves pass through the skin.

This page was last updated at 10:02AM on July 4, 2019.