Doppler Ultrasound Techniques in Placental and Fetal Assessment

Doppler ultrasound has emerged as a pivotal modality for non-invasive evaluation of placental and fetal circulation throughout gestation. By exploiting the Doppler effect to measure blood flow velocity within maternal and fetal vessels, practitioners can assess uteroplacental perfusion, identify early signs of placental insufficiency and monitor foetal well-being. Conventional spectral Doppler provides quantitative indices such as the resistance index and pulsatility index in the uterine, umbilical and fetal cerebral arteries, while colour and power Doppler afford spatial mapping of vascular architecture. Recent advances in ultrafast Doppler imaging have enhanced sensitivity to microvascular flow and enabled discrimination of maternal and fetal components within the placental labyrinth. These techniques inform clinical decisions in pregnancies at risk of intrauterine growth restriction, pre-eclampsia and other complications, and underpin translational research into nutritional, inflammatory and hypoxic challenges across diverse species.

Research from Nature Portfolio

In a non-human primate model of maternal protein restriction, advanced Doppler ultrasound combined with magnetic resonance imaging revealed that severe dietary protein reduction markedly diminishes placental blood flow and maternal–fetal oxygen exchange. These alterations, detected by raised resistance indices and reduced volumetric flow in the umbilical circulation, paralleled increased foetal mortality and growth restriction. Separately, an ultrafast Doppler approach in pregnant rabbits utilised high frame-rate acquisition to map placental microvascular networks (~100 µm vessels) and, by analysing pulsatility on a pixel-by-pixel basis, successfully separated maternal from fetal blood flow. This innovation overcomes the long-standing challenge of discriminating intertwined vascular beds and promises improved diagnosis of placental dysfunction.

Doppler Ultrasound Techniques in Placental and Fetal Assessment publication trend

The graph below shows the total number of articles in doppler ultrasound techniques in placental and fetal assessment across all publications each year (not limited to Nature Index journals).

Technical terms

Doppler ultrasound: An imaging modality that measures the frequency shift of ultrasound waves reflected by moving red blood cells to assess blood flow velocity and direction.

Resistance index (RI): A quantitative measure of vascular resistance calculated as (peak systolic velocity – end diastolic velocity) ÷ peak systolic velocity.

Pulsatility index (PI): A Doppler waveform parameter defined as (peak systolic velocity – end diastolic velocity) ÷ mean velocity, reflecting downstream resistance.

Colour Doppler: A technique that superimposes flow information in colour over a greyscale image to visualise vessel patency and direction.

Power Doppler: An ultrasound mode sensitive to the amplitude of Doppler signals, enhancing detection of low-velocity and microvascular blood flow.

Ultrafast Doppler imaging: A high-frame-rate technique that acquires thousands of frames per second, enabling mapping of small-vessel flow and temporal analysis of pulsatility.

References

1. Impaired placental hemodynamics and function in a non-human primate model of gestational protein restriction. Scientific Reports (2023).
2. Discriminative imaging of maternal and fetal blood flow within the placenta using ultrafast ultrasound. Scientific Reports (2015).
3. To operate or to wait? Doppler indices as predictors for medical termination for first trimester missed abortion. Clinical and Experimental Obstetrics & Gynecology (2021).
4. The uterine artery resistivity index is affected by embryo resorption rate at canine pregnancy diagnosis. Theriogenology (2024).