Fetal circulation in left-sided congenital heart disease measured by cardiovascular magnetic resonance: a case–control study

BACKGROUND The distribution of blood flow in fetuses with congenital heart disease (CHD) is likely to influence fetal growth, organ development, and postnatal outcome, but has previously been difficult to study. We present the first measurements of the distribution of the fetal circulation in left-sided CHD made using phase contrast cardiac magnetic resonance (CMR). METHODS Twenty-two fetuses with suspected left-sided CHD and twelve normal controls underwent fetal CMR and echocardiography at a mean of 35 weeks gestation (range 30-39 weeks). RESULTS Fetuses with left-sided CHD had a mean combined ventricular output 19% lower than normal controls (p < 0.01). In fetuses with left-sided CHD with pulmonary venous obstruction, pulmonary blood flow was significantly lower than in those with left-sided CHD without pulmonary venous obstruction (p < 0.01). All three fetuses with pulmonary venous obstruction had pulmonary lymphangectasia by fetal CMR and postnatal histology. Fetuses with small but apex forming left ventricles with left ventricular outflow tract or aortic arch obstruction had reduced ascending aortic and foramen ovale flow compared with normals (p < 0.01). Fetuses with left-sided CHD had more variable superior vena caval flows than normal controls (p < 0.05). Six fetuses with CHD had brain weights at or below the 5th centile for gestational age, while none of the fetuses in the normal control group had brain weights below the 25th centile. CONCLUSIONS Measurement of the distribution of the fetal circulation in late gestation left-sided CHD is feasible with CMR. We demonstrated links between fetal blood flow distribution and postnatal course, and examined the relationship between fetal hemodynamics and lung and brain development. CMR enhances our understanding of pathophysiology of the fetal circulation and, with more experience, may help with the planning of perinatal management and fetal counselling.