Dopplers are often used to check the placental blood flow, the foetal umbilical blood flow, and blood flow in the heart and brain to ensure everything is normal.
If any restriction to the flow is detected, the doctors can determine if it is caused by a restricted blood vessel, sickle cell anaemia or RH sensitisation. Restricted blood flow in the foetus can cause lower birth weight, impaired development, reduced size, etc.
A special type of Doppler ultrasound called a Transcranial Doppler is used to evaluate the risk of stroke in babies with sickle cell anaemia.
Doppler scans are also recommended in conditions such as:. Doctors ask for a Doppler test when complications or abnormalities are detected in earlier scans that demand extra care for the pregnant woman during the course of pregnancy.
Some of the other common conditions when doctors ask for Doppler scans are:. When the mother is carrying multiples , the pregnancy is considered a high risk one and is monitored regularly with Doppler scans.
This is because such pregnancies have chances for several complications to arise. These complications can be detected early with a Doppler scan. Healthy blood flow in the placenta is essential for normal development of the baby. A Doppler scan is also used if placenta previa low lying placenta is detected. The scan can show the placental position, which can change toward the end of the pregnancy.
Doctors use Doppler scans to determine the blood flow rate in the umbilical arteries and the placenta. There are conditions under which blood flow in the arteries can get restricted, such as the contraction of arteries due to smoking , certain medications, and other lifestyle-related causes.
The contracted arteries offer high resistance to the flow of blood, resulting in improper oxygen and nutrient supply to the foetus. Conditions such as high blood pressure and diabetes can also have a significant effect on this. When the growth rate of the foetus in previous ultrasound scans is not satisfactory, doctors use a Doppler foetus scan for further analysis. A typical ultrasound scan bounces high-frequency sound off the tissues of the body to give a thin two-dimensional image that does not show any movement.
A Doppler ultrasound scan, on the other hand, relies on the Doppler Effect. The phenomenon is a continuous change in the frequency of the bounced sound wave when it hits something that moves, like the blood flow in the arteries. It can measure the difference between blood that is moving away from the probe and blood that is moving towards the probe, as well as its speed.
A Doppler can also detect the heartbeat of the foetus, which other scans cannot. Dopplers are generally used to determine blood flow. During pregnancy, these arteries become stretchy and expand in size to richly supply the uterus with blood.
This physical change allows more amount of blood flow with low resistance through the arteries, so the foetus can be supplied with ample nourishment. If the mother suffers from conditions such as Pre-eclampsia , the blood flow to the artery is restricted. A Doppler scan can be used to detect this condition early on. In conditions where a pregnant woman is carrying twins, a baby appears to be growing slowly, or if the baby is affected by the rhesus antibodies, the doctor would recommend an umbilical artery scan.
Umbilical arteries carry blood from the placenta to the baby through the umbilical cord. A Doppler scan of this artery reveals the amount of blood flow in it and how much nutrients and oxygen the baby is receiving. The scan is performed only if the baby is suspected to be anaemic, the baby is affected with slapped cheek syndrome , or if the baby is affected by rhesus antibodies.
This is a rather uncommon Doppler scan. It is done in the first trimester, along with other tests to look for a chromosomal abnormality in the foetus. Types of Doppler Scan in the Pregnancy Phase. There are different types of Doppler scans that can determine various characteristics, such as the direction of the blood, the velocity of the blood, and the location.
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If forced to continue running, this expectant mother quite likely would eventually collapse, similar to the fetus in a growth environment with absent or reversed end-diastolic flow. The optimal timing of delivery in fetuses with Doppler abnormalities in association with intrauterine growth restriction depends on the underlying cause as well as the estimated gestational age. No adequately powered randomized trials have been performed to determine the optimal time for delivery. In addition to using Doppler ultrasound to assess the umbilical arteries, some physicians historically have assessed the middle cerebral artery in the brain to determine if the fetus is trying to protect the brain in the midst of an oxygen poor environment.
Other physicians also include an assessment of a central vessel called the ductus venosus. The ductus venosus is a portion of the left umbilical vein.
In the fetus, the ductus venosus allows oxygenated blood from the placenta to bypass the liver. In cases where Doppler abnormalities exist because of fetal growth restriction, blood flow in the ductus venosus will significantly increase. Unfortunately, no adequately powered randomized trials have been performed to determine the optimal time for delivery when Doppler abnormalities exist. Joel K. Learn More. What are Doppler Ultrasound Tests? Stories of Hope. Their week ultra sound revealed a large tumor.
Most of us are unaware that the Doppler principle is part of our daily lives, for example, in how we hear the sirens of first responders. Think about the last time you saw an approaching ambulance or fire truck, lights flashing, sirens blaring. The pitch and volume then decrease once the vehicle passes to the point where the sound can no longer be heard when the siren is far enough away. Thus, some providers use the term Doppler velocimetry, the measurement of speed. Check out our post on what to expect at your first visit.
Read stories as told by families who have gone through a fetal diagnosis.
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