We read with interest the article from Dar et al reporting their results in terms of preeclampsia (PE) screening using the 3-dimensional (3D) power Doppler quantification of the vascular indices within the uteroplacental unit during the first trimester of pregnancy.

The vascularization indices provided by this novel ultrasonographic tool have been proven to be highly correlated with the real blood perfusion in vivo. Using this approach, the uteroplacental hypoperfusion in cases of PE has been confirmed in later pregnancy, but, for the first time to our knowledge, the article by Dar et al demonstrates that lower indices can be measured in the first trimester in women who subsequently develop PE.

Even if statistically significant, the observed differences between women with PE and women with unaffected pregnancies, however, seem to be quite limited when considering the results as reported in their Figure 2 with box and whisker plots. This might in part be due to the technique used at the time of 3D acquisition and determination of volume of interest.

Indeed, the so-called sphere sampling method provided by the VOCAL software (Virtual Organ Computer-aided AnaLysis software; GE Medical Systems, Waukesha, WI) in their Figure 1 was applied. With this approach, only a small portion of the uteroplacental unit was evaluated. To standardize the analysis, the sphere was systematically placed around one area containing both intervillous space vessels and spiral arteries. As previously demonstrated by others, applying a multiple biopsy sampling method, the placental vascularization is more heterogenous in women with PE. By targeting only a unique vascularized area in each uteroplacental unit, the authors might have overestimated the vascularization, as measured by the 3D indices, in women with PE.

The quantification of the vascularization with the 3D Doppler tool might be more representative of the true blood perfusion when the largest portion of the uteroplacental unit is included within the volume of interest. In women, the separate study of a large volume of both the placenta and the myometrium is feasible with a high intraobserver and interobserver reproducibility by using the manual multiplanar tracing approach.

Dar et al confirmed the potential great interest of the 3D Doppler for screening PE. We believe, however, that the analysis of a greater proportion of the uteroplacental unit might improve the accuracy of this promising method.