There are tests that look at the fetus, and then there is Doppler, which “listens” to how the blood moves.
This is a specialized ultrasound technique that evaluates blood circulation in specific vessels of the fetus, the placenta, and the uterus.
Doppler gives us valuable information about the baby’s health and development that we cannot obtain from any other ultrasound examination.
This examination is performed by a highly experienced member of our team, specialized in Maternal-Fetal Medicine—a field that combines ultrasound monitoring of the fetus, the assessment of complicated pregnancies, and the performance of specialized intrauterine procedures.
What is a Doppler ultrasound?
Doppler is based on the Doppler effect—the change in the frequency of ultrasound waves when they are reflected by moving objects, in this case red blood cells circulating in the vessels.
By analyzing these changes, we can measure the velocity and flow characteristics of the blood in any vessel we wish to examine.
In obstetrics, Doppler is mainly used to assess three vessels:
Umbilical artery
We measure blood flow from the fetus to the placenta. Abnormal flow in the umbilical artery is one of the most reliable indicators of placental dysfunction and fetal growth restriction.
Middle cerebral artery (MCA)
We measure blood flow in the fetal brain. In cases of hypoxia, the fetus “redirects” blood toward the brain—a phenomenon that is detected early by MCA Doppler before other signs of deterioration appear.
Uterine arteries
We assess blood flow from the mother to the placenta. Abnormal findings in the uterine arteries are associated with an increased risk of preeclampsia and fetal growth restriction.
When is a Doppler examination performed?
Doppler is not a routine examination for all pregnancies—it is indicated in specific situations that require closer monitoring:
- Fetal growth restriction (IUGR)
- High-risk pregnancy—preeclampsia, gestational hypertension
- Reduced fetal movements
- Abnormal findings on the growth ultrasound
- Multiple pregnancy with growth discordance between the fetuses
- Pregnancy after IVF with complications
- History of miscarriage or a previous pregnancy with complications
It is usually performed from the third trimester onward, although in some cases it may be requested earlier.
How is the Doppler examination performed?
The Doppler examination is performed transabdominally, with the probe on the abdomen, just like a standard ultrasound. It is completely painless and safe for the fetus.
No special preparation is required—no fasting and no full bladder. It is simply recommended to avoid strenuous physical activity shortly beforehand so that you are calm during the examination.
How long does a Doppler examination take?
The examination usually takes 20–30 minutes, depending on the number of vessels being assessed and the position of the fetus. It is often combined with a growth ultrasound during the same visit, so the total duration may be longer.
What do the results mean?
Doppler results are assessed based on specific flow indices, such as the resistance index (RI) and the pulsatility index (PI), which are compared with the normal values for the corresponding week of pregnancy.
Abnormal findings may include reduced, absent, or reversed flow in the umbilical artery—findings associated with varying degrees of fetal compromise that determine the frequency of monitoring or the need for preterm delivery.
Each result is always evaluated as a whole, in combination with the ultrasound findings, the clinical picture, and the gestational age.
Frequently Asked Questions (FAQ)
The term “triplex” usually refers to the color Doppler method, which displays blood flow in color on the screen. In essence, it is the same technology, simply presented in a different way. In obstetrics, the two terms are often used interchangeably.
No, Doppler is not a routine examination for every pregnancy. It is indicated when there are specific reasons that justify assessing the fetoplacental circulation. Your doctor will decide whether and when it is needed.
In our clinic, however, it is included in the monitoring process for the majority of our patients, as we believe that early assessment of the circulation can reveal findings that might otherwise go unnoticed.
Not at all—it is completely painless and safe. It uses the same ultrasound technology as standard scans, with no effect on the fetus.
It depends on the severity of the finding and the gestational age. In some cases, monitoring becomes more frequent; in others, the need for early delivery is assessed. The decision is always individualized and based on the full set of clinical data.
The results are available immediately after the examination. Doppler is assessed on the spot during the scan and does not require laboratory processing.
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