Prenatal MRI in Growth-Restricted Fetuses: Early Brain Changes Beyond Doppler Findings: A Retrospective Cohort Study

Background To evaluate fetal brain changes in growth-restricted (FGR) and small-for-gestational-age (SGA) fetuses using diffusion-weighted magnetic resonance imaging (DW-MRI), and to correlate findings with Doppler ultrasound parameters. Methods In this retrospective study, we included singleton pregnancies diagnosed with FGR or SGA who underwent fetal brain MRI after 30 weeks of gestation. FGR was defined based on estimated fetal weight or abdominal circumference < 10th percentile with abnormal Doppler indices, while SGA fetuses had similar biometric criteria but normal Dopplers. Apparent diffusion coefficient (ADC) values were measured in multiple brain regions and compared between groups. Doppler indices and perinatal outcomes were also analyzed. Results A total of 44 patients (30 FGR, 14 SGA) were included. FGR fetuses had significantly higher umbilical artery pulsatility index, smaller biparietal and transverse cerebellar diameters, and lower ADC values in frontal white matter compared to SGA fetuses. ADC values in other brain regions were not significantly different. Lower frontal ADC values (< 1.7 × 10⁻³ mm²/s) were associated with lower 1-minute Apgar scores, lower cord pH, and higher NICU admissions. Conclusion DW-MRI may identify early brain alterations in FGR fetuses before overt clinical signs. Combined with Doppler findings, MRI can enhance risk stratification and guide timing of delivery.