Impairment of the frontal lobe in late-onset fetal growth restriction: is it detectable in fetuses with a normal cerebroplacental ratio?

OBJECTIVES

In fetal growth restriction (FGR), the brain-sparing effect refers to a hemodynamic adaptation that prioritizes blood flow to the brain. The aim of this study was to assess whether fetuses with late-onset FGR have smaller brain structures and evaluate whether the structural impairments of the brain are present even when the cerebroplacental ratio (CPR) is still normal.

METHODS

In this prospective cross-sectional study, ultrasonography was used to measure the frontal antero-posterior diameter (FAPD), occipito-frontal diameter (OFD), biparietal diameter (BPD), sylvian fissure depth (SFD), and insular lobe depth (ILD) in 30 control fetuses and 90 late-onset small fetuses: 30 small for gestational age (SGA) and 60 FGR. The FAPD/OFD, SFD/BPD and ILD/BPD ratios were calculated. The differences in FAPD, ILD, SFD, and their ratios among the study groups were calculated.

RESULTS

Compared to controls or SGA, late-onset FGR fetuses had significantly smaller FAPD (both P < 0.01)and FAPD/OFD ratio ((both P < 0.05)), but there were no differences in FGR between normal and abnormal CPR (P > 0.05). Frontal lobe changes were present in 56.7% (34/60) of all FGR fetuses. In addition, FGR with abnormal CPR was associated with smaller head circumference and OFD relative to controls (P < 0.05). No significant differences were found in ILD, SFD, SF/BPD ratio, or IL/BPD ratio among the four groups (P > 0.05).

CONCLUSION

Ultrasound may be a sensitive and convenient method of detecting changes in the brain in late-onset FGR. Frontal lobe impairment was observed in late-onset FGR fetuses regardless of their CPR status, suggesting that this structural change may be present even in those with a normal CPR.