Postpartum haemorrhage (PPH) Defined as blood loss from the genital tract of 500 mL or more following birth however less than 500 mL in a compromised patient (e.g. a woman with anaemia) can constitute a PPH if it causes symptoms of hypovolaemia. Pre-eclampsia New hypertension presenting after 20 weeks with significant proteinuria. Pulmonary embolism Obstruction of the pulmonary arterial system by a thrombus that has become dislodged and travelled back through the venous return and on to the vessels in the lung. Severe pre-eclampsia Pre-eclampsia with severe hypertension and/or with symptoms, and/or biochemical and/or haematological impairment. Shock A syndrome of impaired tissue oxygenation and perfusion due to a variety of causes and means that the cardiovascular system fails to deliver enough oxygen and nutrients to the tissues to meet metabolic needs. The effect of shock and the associated lack of oxygen will lead to meta- bolic acidosis, cell swelling, necrosis, organ failure and death unless both the symptoms and cause are treated. Shoulder dystocia cephalic vaginal delivery where additional obstetric manoeuvres are required to deliver the fetus after the head has delivered.