Placental MRI shows preservation of brain volume in growth-restricted fetuses who suffer substantial reduction of putative functional placenta tissue (PFPT)

Objective: Recently, a potentially useful diagnostic approach based on MR diffusion-tensor-imaging (DTI) was reported for the estimation of putative functional placenta tissue (PFPT), thus providing direct information about placental function. Yet, the relation between reduced PFPT and the phenomenon of brain-sparing remains unclear. This study aimed to investigate the relation between brain-sparing and reduced PFPT volume, as found in fetuses with intrauterine growth restriction (IUGR).

Methods: A total of 40 consecutive patients with a US-based diagnosis of placental IUGR were examined using fetal MRI. A control group of 78 patients who received fetal MRI, due to non-placental pathologies, was established. A somatic energy index was calculated as I_E=1-(V_brain/V_pfpt) from brain and PFPT volumes measured with DTI in both groups. I_E, V_pfpt, and V_brain were analyzed with respect to the gestational week.

Results: V_brain corrected for gestational weeks was no different between both groups, while V_pfpt was significantly reduced in IUGR patients. I_E was significantly different between both groups and indicated a higher V_brain at a comparable V_pfpt.

Conclusions: Fetuses with IUGR show preserved energetic resources necessary for brain growth. Because I_E drops in IUGR more rapidly as pregnancy progresses, depending on V_pfpt, I_E could prove useful for estimating fetal well-being.