T2*‐Relaxometry MRI to Assess Third Trimester Placental and Fetal Brain Oxygenation and Placental Characteristics in Healthy Fetuses and Fetuses With Congenital Heart Disease

Background Congenital heart disease (CHD) has been linked to impaired placental and fetal brain development. Assessing the placenta and fetal brain in parallel may help further our understanding of the relationship between development of these organs. Hypothesis 1) Placental and fetal brain oxygenation are correlated, 2) oxygenation in these organs is reduced in CHD compared to healthy controls, and 3) placental structure is altered in CHD. Study Type Retrospective case–control. Population Fifty‐one human fetuses with CHD (32 male; median IQR gestational age GA = 32.0 30.9–32.9 weeks) and 30 from uncomplicated pregnancies with normal birth outcomes (18 male; median IQR GA = 34.5 31.9–36.7 weeks). Field Strength/Sequence 1.5 T single‐shot multi‐echo‐gradient‐echo echo‐planar imaging. Assessment Masking was performed using an automated nnUnet model. Mean brain and placental T2* and quantitative measures of placental texture, volume, and morphology were calculated. Statistical Tests Spearman's correlation coefficient for determining the association between brain and placental T2*, and between brain and placental characteristics with GA. P ‐values for comparing brain T2*, placenta T2*, and placental characteristics between groups derived from ANOVA. Significance level P < 0.05. Results There was a significant positive association between placental and fetal brain T2* ( ⍴ = 0.46). Placental and fetal brain T2* showed a significant negative correlation with GA (placental T2* ⍴ = −0.65; fetal brain T2* ⍴ = −0.32). Both placental and fetal brain T2* values were significantly reduced in CHD, after adjusting for GA (placental T2*: control = 97 ±24 msec, CHD = 83 ±23 msec; brain T2*: control = 218 ±26 msec, CHD = 202 ±25 msec). Placental texture and morphology were also significantly altered in CHD (Texture: control = 0.84 0.83–0.87, CHD = 0.80 0.78–0.84; Morphology: control = 9.9 ±2.2, CHD = 10.8 ±2.0). For all fetuses, there was a significant positive association between placental T2* and placental texture ( ⍴ = 0.46). Conclusion Placental and fetal brain T2* values are associated in healthy fetuses and those with CHD. Placental and fetal brain oxygenation are reduced in CHD. Placental appearance is significantly altered in CHD and shows associations with placental oxygenation, suggesting altered placental development and function may be related. Evidence Level 3 Technical Efficacy Stage 3