MR angiography demonstrates a positive correlation between placental blood vessel volume and fetal size

While intrauterine growth restriction is often associated with placental dysfunction or abnormal morphology, the link between fetal weight and the placental delivery capacity of blood has not been studied in detail. The purpose of this study was to investigate the relationship between the fetal placental blood volume (FPBV) and fetal length, fetal weight and fetal head circumference using a non-invasive approach.

Placentas from normal pregnancies terminated with elective cesarean section were included. The entire fetal-side placental vasculature was filled with a solution of a gadolinium-containing contrast agent, followed by magnetic resonance angiography. FPBV was calculated from the complete 3D dataset as the sum of high-intense voxels. Areas that appeared different than the main part of the placenta were marked and evaluated by histology. FPBV of each placenta was compared to the fetal measures at birth: weight, length and head circumference. FPBV was also compared to placental weight at birth.

We found that FPBV correlated linearly with fetal weight (p = 0.02) and fetal head circumference (p = 0.03), but found no correlation between the calculated placental blood vessel volume and the placental weight at birth. Histology revealed no pathophysiological findings in any cases. The marked areas were all those of infarctions or fibrinous sedimentation.

Interestingly, we found a positive correlation between FPBV and fetal size. Fetal size was measured in fetal weight and fetal head circumference. Fetal length did not correlate with FPBV. Further studies are warranted to investigate this relationship in pregnancies with intrauterine growth restriction, and whether MRI angiography (without gadolinium-containing agents) is suitable as a novel diagnostic modality for placental dysfunction.