A case of spontaneous pneumothorax occurring at the end of labour in a healthy 17-year-old primigravida is described. Its occurrence was accompanied by marked surgical emphysema of the face, neck, arms and thorax. The patient had had previous thyroid surgery and was coincidentally found to have bilateral cervical ribs on chest X-ray. Previously described cases are reviewed, and the management discussed. Hypoxia to the fetus is a definite threat, and spontaneous pneumothorax should be considered in the differential diagnosis of chest pain and dyspnoea during delivery. It is a potential extragenital cause of maternal mortality.