Late Gestation Fetal Oxygenation is Associated With Birthweight and Head Circumference in Patients With Cyanotic Congenital Heart Disease

Introduction: Abnormal fetal growth and development are evident in patients with cyanotic congenital heart disease (cCHD). However, the relationship between growth and fetal oxygenation is unknown. We sought to investigate the relationship between fetal hemodynamics and fetal growth in cCHD using fetal cardiovascular Magnetic Resonance Imaging (MRI). Hypothesis: The impaired fetal oxygenation would be associated with diminished fetal brain and body growth in cCHD. Methods: We performed a prospective observational study in fetuses diagnosed with cCHD at our institution from June 2010 to January 2020. Late-gestational fetal cardiovascular MRI was performed in 152 fetuses with cCHD to assess fetal blood flow (phase-contrast MRI) and oxygen saturation (T2 oximetry) in the major fetal vessels to calculate oxygen delivery to the brain and body according to our previously published techniques. Results are provided as medians with IQR and compared with 30 gestational age-matched normal controls using Mann-Whitney U test. A Pearson’s correlation was used to examine the relationships between variables. Results: Compared with normal controls, fetuses with cCHD had significantly reduced birth weight Z-scores [-0.41 (-0.29, 0.84) vs. -0.19 (-0.46, 0.37), p = 0.03], and neonatal head circumference Z-scores [0.1 (-1.75, 0.95) vs. 0.69 (0.1, 1.79), p = 0.003]. As a combined cohort, birthweight Z-score was correlated with fetal oxygen delivery (r = 0.33, p = 0.003), umbilical vein flow (r = 0.2, p = 0.006) and oxygen saturation (r = 0.25, p = 0.02). Birth head circumference Z-score was correlated with fetal cerebral oxygen delivery (r = 0.33, p = 0.01) and ascending aorta oxygen saturation (r = 0.33, p = 0.009). We also found an inverse relationship between ascending aorta oxygen saturation and superior vena cava flow (r = -0.24, p = 0.036). Conclusions: In conclusion, we observed associations between placental function in late gestation and birthweight, as well as cerebral oxygen delivery in utero and head circumference at birth. Our findings are in keeping with the concept that cCHD impacts fetal development through abnormal circulatory physiology and placental function.