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In a Doppler, examination soundwaves are transmitted at a specific frequency into the abdomen and detects the changes in the soundwave frequency of the echoes that are being thrown back. The change in the frequency is due to the soundwave hitting a moving object, this could, for example, be the red blood cells in the blood vessels.

The ultrasound machine can calculate the speed of the red blood cells and show it on the screen with a doppler graph. With this is can read for example the heart frequency, velocity and the index of the resistance in the blood vessel examined.

The resistance is interesting to measure, because a fetus that is lacking, for example, oxygen, it will tend to have a very high resistance in the blood vessels, in the umbilical cord, which can have consequences for the child’s development and well-being.

The Doppler examination is primarily used if there is a suspicion of a growth inhibitory (to see the fetus well-being, even if the weight is low). But it is also used to predict the development of the pregnancy (for example if there should be a risk of pre-eclampsia later in the pregnancy).

If there is a suspicion that the fetus is anaemic, then it is also possible to measure the blood flow, through the blood vessels. Here the velocity of the blood is increased, and the blood will contain less red blood cells, and can, therefore, run faster than normal.

The blood vessels that the doctors are interested in examining are for example:

  • Arteria uterine: This is where the blood vessels from the mother, are running to each side of the uterus, and into the placenta. This examination of both the left and right arteria uterine is done before 24 weeks of pregnancy and can be used to predict if there is a risk for the mother to develop pre-eclampsia later in the pregnancy. The resistance in the blood vessels is increased when there is a risk of pre-eclampsia.
  • Arteria umbilicalis: The blood vessels in the umbilical cord is examined after 24 weeks of pregnancy, to see if the fetus lacks oxygen/poor well-being. The resistance in the blood vessels is usually increased due to the above conditions.
  • Arteria cerebri media: The blood vessels in the child’s heart is examined after 24 weeks of pregnancy. If the child suffers from the lack of oxygen. Then the blood vessels will try and compensate by decreasing the resistance, so that is is possible to get more blood streaming to the brain. This results in a decreased resistance in the arteria cerebri media.

The Doppler examination requires advanced ultrasonic equipment, and it places some great demands on the medical qualifications and experience in the production of a doppler graph, and in the interpretation of these.

The Doppler examination is relevant to get if:

  • If you earlier have had a child with growth inhibitory
  • If you earlier have been through a pregnancy with pre-eclampsia
  • If there is a suspicion of a low fetus growth, stagnated fetal growth due to small symphysis findings or assessment by external examination of your stomach.
  • If there is a suspicion of anaemia in the fetus, for example, due to infections with parvovirus, insemination.
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