Doppler Sonography – Types, Process & Limitations

Doppler Sonography – All You Need to Know

Medically Reviewed By
Dr. Sabiha Anjum (Gynecologist/Obstetrician)
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Recent studies claim that conducting a Doppler sonography to monitor the health of a foetus in high-risk pregnancy can reduce the number of baby deaths and cesarean sections. Let’s take a look at what Doppler sonography is.

What Is a Doppler Sonography?

Doppler sonography or foetal Doppler ultrasound is a technique that is used to measure the flow of blood through the umbilical cord. It checks if the flow to all the parts of the body, including your baby’s brain and heart, is normal. This shows whether the baby is getting all the required nutrients and oxygen or not. Doppler sonography is used to diagnose different problems related to pregnancy.

Mostly, the equipment used to conduct a normal scan is used for a Doppler scan too. The scan also takes place at the same time. Almost all ultrasound equipment comes with a Doppler function.

The person who carries out the scan (or the sonographer) puts a gel on your tummy and moves the transducer, a hand-held device, over it. This device sends sound waves into your womb. These waves bounce off your baby’s blood flow through the circulatory system and umbilical cord. This bouncing back is used to check how your baby is doing.

This scan can take place just after your ultrasound scan, and it takes just a few minutes for this scan to get over. You get the results straight away.

Is Doppler Sonography Safe?

Just like ultrasound scans, Doppler ultrasound in pregnancy is safe as well, when conducted by a trained professional. Opt for a Doppler scan to see if your baby is doing well. Safety is something that you do not need to worry about as there is no risk to you or to your baby. A Doppler scan is performed at 12 weeks for uterine artery flow to predict pre-eclampsia.

Types of Doppler Ultrasound

There are three basic types of Doppler ultrasound scan, and they are:

Continuous Wave or Bedside Doppler

This Doppler scan measures the changes in the pitch of sound waves to analyse the flow of blood through your baby’s blood vessels. The doctor listens to the transducer’s sound and assesses the blood flow. The doctor can tell if the blood flow is less or blocked in an area by analysing this sound. This scan makes use of a device that can check the extent of damage to the blood vessels or the presence of any disease.

Duplex Doppler

Duplex Doppler

The standard ultrasound equipment is used to get a picture of the blood vessels and the surrounding organs. The Doppler sound is made into a graph by a computer, which shows the speed and the direction of blood flow through the vessels.

Colour Doppler

Colour DopplerThis method makes use of the standard ultrasound equipment to take pictures of your baby’s blood vessels too. A computer transforms the sounds of the scan into colours. These colours are overlaid on the pictures of the blood vessels, and they show the direction and speed of blood flow through the blood vessels. Power Doppler is a type of colour Doppler which helps doctors get some difficult images that are not possible to obtain using the standard procedure. A power Doppler scan is often recommended to see the flow of blood through vessels present in solid organs.

Why Is Doppler Sonography Done?

Doctors usually recommend baby-heartbeat Doppler sonography when your pregnancy requires some extra care. You may need extra care in the following cases:

  • Your BMI (Body Mass Index) is high or low
  • You are carrying multiples
  • You have diabetes or high blood pressure or some other existing medical condition
  • Your baby has rhesus antibodies
  • You contract human parvovirus B19 or slapped cheek syndrome within the first 20 weeks of your pregnancy
  • You are a smoker
  • The rate of baby’s growth is slow or unhealthy
  • You previously gave birth to a small baby
  • You experienced a miscarriage in the past or gave birth to a stillborn baby
  • If your baby has intrauterine growth restriction and is growing at a very slow rate

How Is Doppler Sonography Done?

How Is Doppler Sonography Done?

The sonographer uses a hand device called a transducer to check different areas depending on the information he/she is looking for. A Doppler ultrasound test can also be done by a radiologist. The test is usually done in an ultrasound room, and you would be asked to remove any jewellery that might affect the result of the scan.

You will need to lie on your back or on your left side and ensure that your belly is exposed. The gel will be applied to your belly. You will need to stay still until the test is over. Your doctor may ask for one of the following Doppler scans:

Uterine Artery Doppler Scans

The arteries carrying blood to your womb are known as uterine arteries and this Doppler test is conducted to see if sufficient blood is reaching your baby through the placenta.

If enough blood is not going through the placenta, it affects the growth of the baby as oxygen and nutrients fail to reach the baby through the umbilical cord.

Your doctor will recommend the uterine Doppler scan if you have a chance of getting affected by pre-eclampsia, a condition that is characterised by high blood pressure and affects the way the placenta works.

Umbilical Artery Doppler Scan

If you are carrying twins, your baby has rhesus antibodies, or if your baby is showing a slow growth rate, an umbilical artery Doppler scan would be recommended.

This scan analyses the blood flow from the baby to the placenta via the umbilical cord. If the sonographer finds any issue with this scan, he/she might request other Doppler scans to check the flow of blood in your baby’s brain and his main artery, the aorta.

If the scan reveals that your baby is not getting enough nutrients, an early delivery might be prescribed.

Doppler Sonography Test Preparation

There is no preparation required for Doppler scans. Just make sure you are carrying all the reports of previous Doppler scans if any, and all your doctor’s prescriptions.

Limitations of Doppler Ultrasound

There are certain limitations of a Doppler Ultrasound:

  • Vessels present deep inside your baby’s body are more difficult to analyse than the superficial ones. MRI and CT scans are required to see these deep vessels properly
  • Smaller vessels, at times, become difficult to evaluate
  • If calcifications are present in the blood vessels as a result of atherosclerosis, they can obstruct the beam of ultrasound
  • The ultrasound beams are often not able to differentiate between blood vessels that become narrow and the ones that are completely closed. The presence of a small opening with weak blood flow can give undetectable signals

Can You Use Doppler at Your Home?

Can You Use Doppler at Your Home?

Portable Doppler scan machines are available, and you can hire or buy one of these to listen to your baby’s heartbeat. This is also known as a pocket foetal Doppler. However, doctors recommend that mothers do not use one at home.

The results offered by these handheld Dopplers are hard to analyse. You may end up listening to the sound of blood flowing through your artery or the placenta and mistake it for your child’s heartbeat.

Getting the scan done by a professional and going for your antenatal appointments is a surer way of knowing how your baby is doing. So, make sure that a sonographer or a doctor is conducting the test on you.

Conclusion: A Doppler scan helps you and your doctor know if the baby is growing well. The scan is risk-free and does not require any preparation. However, it is important that a trained sonographer conducts the scan and your doctor analyses the results.

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