In pregnancy the cardiac output and blood volume increase from the second month up to the thirtieth week to 30-50% above the normal levels. This, along with the increased metabolic work, produces the physical signs of warm extremities, a tachycardia with a large-volume pulse and a slight rise in venous pressure. The apex beat is displaced, owing partly to cardiomegaly and partly to a raised diaphragm. The increased blood flow produces a pulmonary systolic murmur and a third heart sound. The diastolic blood pressure is lower owing to vasodilatation. The added burden of pregnancy on the cardiovascular system can make underlying, otherwise latent, disease clinically apparent. Ten per cent of maternal deaths in England and Wales are due to heart disease. This is usually rheumatic or congenital in origin, but any heart disease can be seen in pregnancy. Moderate to severe mitral stenosis can cause breathlessness early in pregnancy and may lead to pulmonary oedema later in pregnancy. Pregnancy should be avoided in severe mitral stenosis or delayed until after valvotomy. Termination may be necessary in a severe case occurring before the sixteenth week. Most cases of congenital heart disease have been corrected by the time women reach the reproductive age. However, patients with small and uncomplicated septal defects usually tolerate pregnancy well. Patients with prosthetic valves are usually on anticoagulant therapy. This may require a change to heparin because warfarin can cause fetal abnormalities. Patients with pulmonary hypertension of any aetiology have an extremely high mortality (up to 50%) either during or immediately after delivery, and termination should be considered. Post parium, or late in pregnancy, a cardiomyopathy of uncertain aetiology is sometimes seen. There is also a rise in thromboembolic complications of cardiac disease owing to the hypercoagulability that exists post partum. Sepsis is a risk during delivery, and patients with heart disease may be at risk of developing infective endocarditis.