To evaluate the placental micro-vascular circulation by microvascular flowing imaging (MVFI) method, and to explore the clinical value of microvascular index (MVI) for the diagnosis of fetal growth restriction (FGR).

A total of 21 fetuses at 24-34 weeks of gestation at the Peking Union Medical College Hospital from October to November 2019 were enrolled in this study, including 7 fetal growth restriction (FGR) fetuses, and 14 normal fetuses as control group. The fetuses of the two groups were matched according to the gestational weeks at the ratio of 1∶2. Fetal biometry parameters were measured and the placenta was observed by two-dimensional ultrasound.Uterine artery pulse index (UtA-PI), middle cerebral artery pulse index (MCA-PI), and umbilical artery S/D ratio were evaluated by color and pulse-wave Doppler. The placenta mico-circulation was displayed by the MVFI method and MVI was measured.

The study included 14 normal fetuses and 7 FGR fetuses. Compared with the control group, more placenta in the FGR group manifested as thickened and heterogeneous with decreased MVI and increased UtA-PI. There was statistically significant difference in placental mean MVI between two groups (P=0.044). Besides, a trend towards significant negative correlation was observed between MVI and placenta thickness, although this was not statistically significant (r_s=-0.35, P=0.065). MVI had a higher specificity (100%) in the prediction of FGR.

MVFI can display the micro-circulation of the placenta, and provide a direct and quantitative assessment method for placental perfusion.

Ultrasonography; Microvascular flowing imaging; Placenta; Fetal growth restriction