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Doppler Ultrasound

Doppler ultrasound is useful in monitoring the blood flow of a fetus and to check various other aspects of the unborn baby’s and mother’s health. This technique uses reflected sound waves to observe the flow of blood through blood vessels.

During a Doppler ultrasound scan a transducer, which sends and receives sound waves, is passed over the stomach of the mother. This painless procedure is effective in gathering information about the blood flow of the fetus, which can be processed by a computer in the form of a graph or a picture.

When sound waves bounce off blood cells there is a change in the pitch of the reflected sound waves. This is called the Doppler effect. The pitch remains the same if there is no blood flow.

While Doppler ultrasound is mostly used in pregnancy to monitor the blood circulation of the fetus, it can also be useful in detecting blood circulation in the uterus and placenta. The information gathered can often be vital in reducing interventions upon birth.

There are four main types of Doppler ultrasound. Continuous wave Doppler, also known as ‘bedside’, provides information about blood flow through the change in pitch. Duplex Doppler is able to produce a computerised picture of blood vessels and surrounding organs as well as useful information about the direction and the speed of the blood flow.

Colour Doppler, like its name suggests, produces coloured pictures on a computer. Power Doppler is the most sensitive type of Doppler ultrasound, at up to five times more sensitive than colour Doppler. This type of Doppler is best used to detect blood flow within organs.

It is also possible to use more than one Doppler technique together in evaluating the health of the fetus. This may provide greater information on the direction and the speed of the blood flow than if just one Doppler method was used.