OBJECTIVE: Prenatally compromised fetal head growth leading to smaller brain volumes (BV) is a risk factor for neurodevelopmental delay in children with CHD. Little is known about the dynamics of fetal head growth in different types of CHD. Aim of this study was to characterize fetal brain growth in relation to the type of CDH and associated cardiovascular dynamics.

STUDY DESIGN: 89 chromosomally normal fetuses with isolated CHD had head circumference (HC), calculated BV (HC3/6_2), fetal cephalization index (CI_HC/EFW), growth potential (GP), middle cerebral artery Pulsatility index(MCAPI) and central hemodynamic measurements. Z-scores for these parameters were compared between
cases and 1535 normal singleton controls. CHD was grouped as follows: group 1: transposition of the great arteries (TGA, n_7), group 2: Hypoplastic left heart and critical aortic stenosis with retrograde aortic flow (n_55), group 3: (right sided lesions) pulmonary stenosis, Tetralogy of Fallot, Tricuspid atresia (n_ 14), group 4: Left
ventricular outflow obstructions with net antegrade isthmic flow (n_13).

RESULTS: HC, BV and GP were lower in groups 1 and 2 (all p_0.001). BVs were smaller in group 1 (_1.98 vs_0.72, p_0.001). The MCAPI z-score was significantly decreased in groups 2 and 4 (p_0.001 compared to controls) with the lowest median values in the latter (_0.65 vs. _1.51, p_0.04). MCA PI z-score was not correlated with head growth in group 2 but was inversely correlated to BV in group 4 (p_0.04).

CONCLUSION: Transposition of the great arteries and left sided CDH leading to isthmic blood flow reversal are associated with significantly smaller head size. TGA is not associated with MCA brain sparing and delayed brain growth probably results from central switching of nutrient streams. Left sided lesions are associated with MCA brain sparing but head growth is only spared when net antegrade flow in the aortic isthmus can be maintained. Prenatal evaluation of central hemodynamics in CDH may become essential for predicting neurodevelopmental risks and potentially critical to direct prenatal interventions