This ultrasound scan is one of the most important tests of your pregnancy. It can be done from 28 until 36 weeks (preferably at 32 weeks of pregnancy), unless there are reasons for it to be done in some other time. It is usually combined with the growth scan. It is performed from the tummy.
What are the purposes of the Dopplers scan?
evaluation of blood flows in specific vessels.
It has been scientifically proven that by asseesing the blood flow pattern in specific vessels of the baby's body, we can draw useful conclusions about the oxygenation and fetal well- being status. The vessels interrogated are the umbilical arteries, the middle cerebral artery and the ductus venosus. Occasionally, the uterine arteries blood flow pattern in the mother's body need to be interrogated as well.
drawing of conclusions about the fetal well- being.
The umbilical cord connects the placenta to the baby and supplies it with the necessary oxygen and nutritional elements. A normal blood flow in the umbilical arteries is a proof that this process has not been disturbed.
Several conditions may interfere with this physiologic process. In this case, evidence of abnormal blood flow pattern in the umbilical arteries is present and can vary in severity.
If an abnormal blood flow in the umbilical artery is found, we will examine the flow in the middle cerebral artery, a brain vessel, because studies have shown that the flow in this vessel becomes abnormal at a later time the umbilical artery does. If the middle cerebral artery flow is also disturbed, that means that the baby is making efforts to adapt in a lack of optimum oxygenation environment. In case it is normal, though, that might signify that, for the time being, the fetus is compensating well.
The third vessel interrogated is called ductus venosus and is found in the baby's liver. Abnormal flows in this vessel are considered to appear after flows become abnormal in the previous two vessels. Therefore, if a disturbed flow is found in this vessel, then that means that the situation is getting critical.
All the above, merely represent a simplified approach, purely for descriptive reasons. Under certain circumstances, exceptions exist, but the general rule still applies. In the same context, the interpretation of findings is similar, albeit a little bit different, in twin pregnancies that share the same placenta (monochorionic).
Important role play other factors that are always taken into account. These are the gestational age, the estimated fetal weight, the amniotic fluid volume etc. This is the reason why, usually, the Dopplers scan is done in combination with a growth scan. In any case, after the scan, an extensive discussion with the couple will follow about the findings and their meaning, so everything is absolutely clear.