A uterine artery Doppler scan is a specialized ultrasound examination performed during pregnancy. This non-invasive procedure assesses blood flow within the uterine arteries, which are the main vessels supplying blood to the uterus, placenta, and fetus. It helps healthcare providers understand the efficiency of blood circulation between mother and baby.
Understanding the Uterine Artery Doppler
Doppler ultrasound technology uses sound waves that bounce off moving red blood cells to measure the speed and direction of blood flow. In a uterine artery Doppler scan, this technique is specifically applied to the uterine arteries, located on either side of the uterus. The sound waves are converted into images and graphs that show blood flow patterns.
During the scan, a gel is applied to the abdomen, and a transducer (a small, handheld device) is moved gently over the skin. The procedure is painless and typically takes around 5 to 45 minutes to complete. This ultrasound is safe for both the pregnant individual and the baby, as it does not involve radiation.
Purpose of the Scan
The primary purpose of a uterine artery Doppler scan is to assess the health of the placental blood supply, which is important for delivering oxygen and nutrients to the fetus. It helps identify pregnancies that may be at an increased risk for certain complications. One significant condition it helps screen for is preeclampsia, a pregnancy disorder characterized by high blood pressure, typically developing after 20 weeks of gestation. Preeclampsia can lead to serious health issues for both the mother and the baby, including impaired liver or kidney function for the mother, and severe growth restriction for the fetus.
The scan also helps identify or monitor fetal growth restriction (FGR), where the baby does not grow as expected. FGR is often linked to placental insufficiency, meaning the placenta is not functioning adequately to support the baby’s growth. By measuring the resistance to blood flow in the uterine arteries, the scan indirectly measures how well the placenta is developing and delivering blood, nutrients, and oxygen to the fetus. High resistance can indicate that placental development is not optimal.
What the Results Indicate
Normal uterine artery Doppler results show low resistance to blood flow, indicating blood flows easily to the uterus and placenta. This suggests the placenta is developing well and supporting the baby’s healthy growth. A normal result also indicates a lower likelihood of developing conditions like preeclampsia.
Conversely, abnormal results show high resistance to blood flow or the persistence of an “early diastolic notch” in the waveform. In a healthy pregnancy, this notch disappears by 18-20 weeks of gestation as the spiral arteries remodel to become low-resistance vessels. A persistent notch or high resistance suggests blood faces increased resistance to flow to the womb, potentially due to inadequate remodeling of the spiral arteries.
While an abnormal result indicates an increased chance of complications like preeclampsia or fetal growth restriction, it does not guarantee these conditions will occur. About 1 in 4 individuals with raised resistance may develop one of these conditions. If abnormal results are found, closer monitoring, such as more frequent ultrasound scans to check fetal growth and regular blood pressure checks, may be recommended.