Hypoplastic left-heart syndrome and critical aortic stenosis with severely restricted or intact foramen ovale are associated with high neonatal mortality and poor long-term outcome. Despite accurate foetal diagnosis and successful postnatal catheter-based and surgical intervention, the 1-month survival rate is about 33%. Changes in pulmonary vascular architecture resulting in pulmonary hypertension result in important long-term morbidity. Prenatal relief of left atrial and pulmonary hypertension may promote normal pulmonary vascular and parenchymal development and improve short- and long-term outcomes. Foetal atrial balloon septostomy, laser perforation, and stenting of the foetal interatrial septum are the current options for foetal therapy. This paper provides an overview of foetal diagnosis, selection of patients for foetal intervention, and interventional techniques, and also reviews the current status of foetal and postnatal outcomes after intrauterine intervention.