Colour Doppler Scans

What is a Doppler scan?

A Doppler scan measures the blood flow through the umbilical cord and around different parts of your baby’s body, such as his brain and heart. This helps to show whether the baby is getting all the oxygen and nutrients it needs via the placenta. You can have a Doppler scan at the same time as a normal scan, as it uses the same equipment. Most ultrasounds have a Doppler function. Doctor (Radiologist)will put some gel on your tummy and move a hand-held device (transducer) over your skin. The transducer sends out sound waves that bounce off the blood flow to your baby’s body via the cord, as well as his blood circulation system. This creates an image on a screen showing the Doctor how the blood is flowing. It gives a good idea of how your baby’s doing. The Doppler scan will take just a few minutes during your regular ultrasound scan.

Are Doppler scans safe?

As with all ultrasound scans, Doppler scans are safe in trained hands. When carried out by a trained Doctor, a Doppler scan helps to give a clear picture of your baby’s health and wellbeing. Doppler scans should not be used before 24 weeks. But used properly, Doppler scans pose no risk to your baby in the second and third trimesters.

Why might I need a Doppler scan?

Your doctor may recommend a Doppler scan if you need extra care during your pregnancy, for example if:

you have a low or high BMI
you’re carrying twins or more
you have an existing medical condition, such as diabetes or high blood pressure
your baby is affected by rhesus antibodies
you smoke
you catch Infections in the first 20 weeks of your pregnancy
your baby isn’t growing at a healthy rate
you’ve previously have a small baby
you’ve previously experienced a late miscarriage or suffered the loss of your baby at birth
Another reason for having a Doppler scan is if your baby is small for dates. The scan can look at whether the placenta is working normally and delivering enough oxygen and nutrients to your baby.

What will happen during a Doppler scan?

Your Doctor will check different areas, depending on what information he needs about your pregnancy and baby.

Uterine artery Doppler scans

Uterine arteries are the vessels that carry blood to your womb (uterus). A uterine artery Doppler scan checks that enough blood is reaching the placenta.
Your baby needs plenty of nutrients and oxygen to grow at a healthy rate. Therefore, the walls of your uterine arteries should be stretchy, to allow as much blood through as possible.
In pregnancy, these normally small arteries increase in size to allow more blood through. This is called low resistance.
If blood can’t get through to the placenta easily enough, your baby may not get the nutrients and oxygen he needs via the umbilical cord. You may have a uterine artery Doppler scan if you have a high chance of developing pre-eclampsia, which affects how well the placenta work

Umbilical artery Doppler scans

If your baby seems to be growing slowly, is affected by rhesus antibodies, or you’re carrying twins, you may be offered a different type of Doppler.
This is called an umbilical artery Doppler, and it looks at the blood flow from your baby, via the umbilical cord, to the placenta. This is a very safe and effective way of finding out whether your baby is getting everything it needs from the placenta.
If any issues are found during an umbilical artery Doppler scan, your obstetrician may request additional Doppler scans to look at the blood flow in your baby’s brain and his aorta, which is the main artery in his body.
Alternatively, she may ask that you visit her a couple of times a week for more umbilical artery Doppler scans.
These will check that your baby’s healthy and help you and your doctor to decide the best time and place for you to give birth.
It’s perfectly safe for your baby to have frequent Doppler scans. The benefits of having lots of scans to monitor your baby’s health outweigh any potential risks.
If any of the scans show that your baby isn’t getting enough nutrients or oxygen, your obstetrician may advise you to give birth early.
It’s a different picture if you just happen to be carrying a small baby. A small baby with a normal blood flow via the umbilical cord is probably getting all the nutrients it needs.