Pulmonary hypertension is defined by a mean pulmonary artery pressure of greater than 25 mmHg at rest or 30 mmHg with exercise. It can occur in association with a variety of medical conditions. The most serious elevation in pulmonary artery pressures are seen in a group of conditions that share the histological entity of plexogenic pulmonary arteriopathy. Pulmonary hypertension may be missed or diagnosed late in the course of the illness. It is associated with a poor prognosis. Pulmonary hypertension carries a significant risk to mother and child during pregnancy and pregnant women with pulmonary hypertension require careful monitoring within the framework of a multidisciplinary team. Specific targeted therapy for pulmonary hypertension may be required during pregnancy. Many agents are contraindicated because of risks of teratogenicity or secretion into breast milk. The optimum mode of delivery is not clear but early input from the high-risk obstetric anaesthesia team is essential.