Prenatal diagnosis of congenital heart disease is now firmly established. Large series have confirmed diagnostic accuracy for a wide range of cardiac lesions.1 Diagnosis of some types of congenital heart disease during fetal life provides a potential opportunity for intervention before birth. The rationale for prenatal cardiac intervention for congenital heart defects is compelling. Some congenital heart lesions, particularly those characterised by left or right heart obstruction, are now recognised to be “progressive” with increased severity later in gestation.2 3 If intervention can be undertaken early enough during fetal life then the deterioration which would otherwise have occurred later in gestation should be averted, translating into a better outcome for affected babies. Prenatal intervention for structural cardiac defects has been undertaken with technical success for a number of different cardiac lesions, including critical aortic stenosis,4 5 6 7 8 hypoplastic left heart syndrome with an intact or severely restrictive atrial septum9 and pulmonary atresia with intact ventricular septum.10 11 Such interventions are now feasible with high rates of technical success at an early stage in pregnancy. It would be expected that if the rationale for prenatal intervention is correct, then technical success would be mirrored by a dramatic improvement in outcome. For any intervention being undertaken during fetal life, the potential adverse effects of disturbing the intrauterine environment, should be outweighed by improved fetal cardiac development and postnatal outcome. Procedural complications, precipitation of preterm delivery,12 intrauterine death and maternal complications are therefore crucial in evaluating the overall benefit of such interventions to judge whether prenatal intervention is “worth it”.

It should also be emphasised that prenatal intervention is only being considered for a small minority of the whole population of fetuses diagnosed with congenital heart disease. At the Evelina Children’s Hospital, 855 fetuses were …