Purpose or Case Report: Diffusion weighted images (DWI) have the potential to provide valuable information on the diffusion and perfusion properties of the human placenta and therefore has the capability for detection of early developmental fetal anomalies. The purpose of this study was to determine if DWI of the placenta demonstrates differences between fetuses with and without central nervous system (CNS) abnormalities.
Methods & Materials: After REB approval was obtained, 1.5 T Fetal MRI of 57 singleton pregnancies (mean gestational age 21 weeks 5 days) were retrospectively analyzed, 39 with CNS morphologic abnormalities and 18 controls without morphologic abnormalities. On DWI (b values 0-1000 s/mm²) the slice that displaced the largest surface of placenta was selected and the apparent diffusion coefficient (ADC) maps were reconstructed. Two ADC quantification methods were performed 1)manually outline the entire surface of the placenta and, 2) 3 regions of interest (ROI) of 79 mm2, in both borders and center of the placenta. Measurements were compared with the presence or absence of CNS fetal abnormalities. Wilcoxon tests were used.
Results: There was significant discrepancy between the two ADC quantification methods (p<0.0001).The ROI measurement method demonstrated significant correlation (p = 0.002) between low ADC and presence of fetal CNS abnormalities compared to controls. However, with the manually outlined method, there was a lack of significant association between low ADC and CNS abnormalities (p=0.1).
Conclusions: The quantification of DWI of the placenta in fetal MRI suggests that the presence of fetal CNS abnormalities is associated with restricted diffusion and reduced ADC values of the placenta using the ROI ADC quantification method. Therefore in the pathologic placenta, DWI and ADC mapping have the potential to quantify early changes, even in the absence of gross structures anomalies. The differences between the two ADC quantification methods suggest inhomogeneity of the ADC values with the large ROI.

Placental DWI has a promising role on the evaluation of early placental anomalies and could have an impact in prediction of CNS fetal abnormalities.