Fetal brain development in fetal growth restriction using MRI: a systematic review

Area of Science:

• Neuroscience
• Radiology
• Developmental Biology

Background:

• Fetal growth restriction (FGR) impacts fetal development, with potential effects on the brain.
• Magnetic Resonance Imaging (MRI) offers insights into fetal brain development.

Purpose of the Study:

• To systematically review and compare fetal brain development in FGR versus appropriate for gestational age (AGA) fetuses using MRI.
• To identify specific differences in brain volumetrics, biometrics, diffusion, metabolites, and oxygenation.

Main Methods:

• Systematic literature search of PubMed, Embase, Cochrane Library, and Web of Science (1985-2023).
• FGR defined by estimated fetal weight (EFW) < p10 and/or abdominal circumference (AC) < p10, or 20% reduction in EFW/AC.
• Meta-analysis of volumetric, biometric, apparent diffusion coefficient (ADC), 1H-MRS metabolite, and oxygenation data.

Main Results:

• Twenty-nine studies included; 13 used the Delphi consensus definition for FGR.
• FGR fetuses showed significantly reduced total brain volume (MD -30.84 cm³, p<0.01) and cerebellar volume (MD -2.24 cm³, p<0.01) compared to AGA fetuses.
• Significantly lower ADC values observed in multiple brain regions (FWM, OWM, TWM, thalami, CSO, basal ganglia, pons, cerebellum) in FGR fetuses.
• Reduced N-acetyl aspartate (NAA): Choline (Cho) and NAA: Creatine (Cr) ratios in the frontal lobe and central brain tissue of FGR fetuses.
• No significant differences in fractional moving blood volume, superior sagittal sinus venous oxygenation, or T2* in the fetal brain.

Conclusions:

• MRI reveals significant differences in brain development between FGR and AGA fetuses, including smaller volumes and altered diffusion characteristics.
• Findings suggest potential alterations in brain maturation and cellular integrity in FGR fetuses.
• Further large-scale studies are needed to correlate these MRI findings with long-term neurocognitive outcomes and to compare brain-sparing FGR fetuses with controls.