Fetal MRI study of brain differences in early-onset fetal growth restriction versus healthy controls at 30 weeks of gestation.

Objective: To identify volumetric and diffusion-related brain differences expressed as apparent diffusion coefficient (ADC) values between early-onset brain-sparing fetal growth restriction (FGR) and healthy controls using magnetic resonance imaging (MRI) at 30 weeks of gestation. Method: This prospective, observational, monocenter cohort study included singleton pregnancies with early-onset brain-sparing FGR at the University Medical Center Utrecht. FGR fetuses were compared to healthy controls from the Utrecht YOUth Cohort. Fetal MRI of the brain was performed including T2-weighted and diffusion weighted imaging (DWI) sequences. We measured 2D biometrics, 3D volumetrics using BOUNTI, and ADC values in multiple brain and placental regions. Values were corrected to 30 weeks of gestation. Results: The study included 26 FGR fetuses at gestational age (GA) 26.3-32 weeks and 71 controls at GA 30.1-34 weeks. At 30 weeks, total brain volume (TBV) was significantly smaller in FGR (144.2 ± 11.5 vs 166.9 ± 17.5 milliliters, p < 0.001). After dividing all absolute volumes by TBV, only cerebellar volume remained significantly reduced (0.045 [0.00] vs 0.048 [0.01], p = 0.006). ADC values were lower in all brain regions except the cerebellum. Placental ADC values were also significantly lower in FGR. Conclusion: Altered brain development in brain-sparing FGR is already present at 30 weeks of gestation. Lower brain volumes and ADC values may reflect the effects of altered perfusion, chronic hypoxia and microstructural changes in the brains of FGR fetuses. Future studies linking these MRI findings to long-term neurodevelopmental outcomes will aid in more personalized prognoses and might also inform the timing of delivery, ultimately enhancing clinical decision-making.