Acute cardiac arrest during pregnancy is a rare but devastating event. Major causes are haemorrhagic, septic or anaphylactic shock, trauma, pulmonary or amniotic fluid embolism, and congenital or acquired cardiac disease. We present a case of massive intrathoracic migration of viscera through a left diaphragmatic hernia in a pregnant multipara, causing acute obstructive shock and cardiac arrest. Complications of intrathoracic herniation occur when the intruding viscera cause left lung and cardiac compression or mediastinal "tamponade" with decreased venous return. Intrathoracic strangulation of viscera is also common and may cause ischaemia, gangrene and eventual perforation. Sudden cardiac arrest as first sign of left diaphragmatic rupture during pregnancy, however, has rarely been described. In contrast with our patient, this catastrophic event is mostly seen in nulli- and primipara with a known congenital left diaphragmatic defect. Management of a diaphragmatic hernia depends on the clinical presentation and the period of gestation during which it is detected. Despite prolonged resuscitation with more than 1 hour of chest compressions, our patient recovered completely.