Study on ultrasound microangiography of placenta in fetal growth restriction

Reduced placental microvascular perfusion is the most important cause of fetal growth restriction (FGR), yet there are currently no effective tools available for assessing placental microcirculation. Ultrasound microangiography is an emerging technology capable of imaging vessels at the micron level. Currently, there is no research on the application of ultrasound microangiography technology for assessing placental microcirculation. This study innovatively explores the feasibility and practicality of using this new technology to evaluate microvascular changes in the placenta in cases of FGR.

Ultrasound microangiography was used to image the microvascular structure and quantitatively analyze microvascular density in 10 FGR placentas and 10 normal placentas from Sprague-Dawley rats. Doppler ultrasound measurements were performed on the uterine arteries, the fetal umbilical arteries, and the middle cerebral arteries of pregnant rats. Placental area and thickness were measured, and hematoxylin and eosin (H&E)-stained placental sections were analyzed to assess the uterine spiral artery wall-to-lumen ratio. Histological determination of placental microvascular density served as the standard for validation.

In FGR cases, the remodeling of the uterine spiral arteries was obstructed, with the placenta exhibiting thinning and increased area. Both placental and fetal blood flow dynamics were altered. Using ultrasound microangiography, real-time dynamic imaging of blood flow from the large placental vessels to the micro-branching vessels was achieved. The shapes of the microvessels were rapidly visualized and reached peak visibility, displaying microvessels with slower flow rates. The boundaries between the microvessels and the placental background were sharply defined, and the placental vasculature formed an orderly, detailed vascular tree. Quantitative analysis of microvascular density in FGR placentas revealed a significant reduction compared with the control group (P < 0.01), a finding further confirmed by immunohistochemistry.

Ultrasound microangiography demonstrates significant advantages in visualizing and quantifying the microvascular features of FGR placentas, enhancing the diagnostic capability for placental vascular diseases in FGR. This new technology provides a novel approach to the prenatal diagnosis of FGR.