Abstract Aim To investigate the development of fetal brain volumes and their association with cerebral oxygenation in fetuses with major congenital heart defects (CHD) compared to healthy controls during the third trimester. Methods This prospective longitudinal magnetic resonance imaging (MRI) study included fetuses with major CHD and healthy controls. CHD cases were categorized into three groups based on cardiac anatomy: right-sided defects, left-sided defects, or transposed great arteries. Repeated MRI scans were performed at 28, 32, and 38 weeks of gestation. Total and regional brain volumes (cortical grey matter, white matter, and deep grey matter) were quantified using automated segmentation of 3D-reconstructed T2-weighted images. Whole-brain oxygenation was assessed using T2* relaxometry. Mixed-effects models were used to compare brain volumes and oxygenation trajectories between CHD and control groups and to examine their associations. The models accounted for gestational age at the time of the scan, fetal sex, and repeated measures within individual subjects. Results We analyzed 112 MRI scans from 20 fetuses with CHD (6 with right-sided defects, 5 with left-sided defects, and 9 with transposed great arteries) and 23 healthy controls. Overall, total and regional brain volumes were similar between fetuses with right- or left-sided defects and controls from 28 to 38 weeks. Fetuses with transposed great arteries had 7.5% (95% confidence interval CI: 1.8% – 12.9%) lower total brain volume compared to controls, along with reduced white matter and deep gray matter volumes (-8.6%, 95% CI: -2.9% to -14.0%, and -7.3%, 95% CI: -1.9% to -12.3%, respectively). Whole-brain oxygenation declined by 3.1% (95% CI: 2.3% – 3.9%) per week, with no significant differences between CHD groups and controls (all p 0.2). No significant effect of whole-brain oxygenation on total brain volumes was observed in any group (p = 0.9). Conclusion Fetuses with right- or left-sided CHD exhibit normal brain growth trajectories from 28 to 38 weeks of gestation. In contrast, fetuses with transposed great arteries show reduced total brain volume, white matter, and deep gray matter volumes. Whole-brain oxygenation declines similarly across all groups, with no observed relationship between brain volume and oxygenation, as measured by T2* relaxometry.
Hellmuth et al. (Sat,) studied this question.