Antiphospholipid syndrome (APS) had been previously diagnosed in three pregnant women aged 32, 27 and 36 years, respectively. All three of them were using low-molecular weight heparin for the prevention of thromboembolic complications. The first two women were admitted because of foetal growth retardation. In the first patient, either HELLP syndrome or exacerbation of APS was suspected. A caesarean section was performed due to foetal distress. The patient's condition deteriorated further postoperatively. Multiple infarctions in liver and placenta were identified. Catastrophic antiphospholipid syndrome (CAPS) was diagnosed. Despite intensive medical treatment including anticoagulation the patient died of massive pulmonary embolism. The second patient suffered from thrombocytopaenia, disturbances in hepatic function and epigastric pain. CAPS was diagnosed. The condition improved after treatment with glucocorticoids, but because of a poor foetal prognosis, delivery was induced and a lifeless son was born. The third woman was admitted due to pyelonephritis. Shortly thereafter, symptoms of HELLP syndrome developed and she was administered glucocorticoids. Hepatic infarcts and petechiae developed, indicating CAPS. Delivery was induced and a girl was born. Glucocorticoid treatment was resumed and combined with immunoglobulins and plasmapheresis. The patient recovered and was discharged together with her daughter. CAPS is a life-threatening variation of APS. It is characterised by multiple thromboses and rapidly progressive multi-organ failure. Mortality is high, but seems to diminish with treatment by immunosuppressive therapy. In pregnancy, clinical signs of CAPS are similar to those of HELLP syndrome. Since the treatment for HELLP syndrome is different from CAPS, a correct diagnosis is essential. Because of the rarity of this condition in combination with high rates of perinatal and maternal mortality, care for pregnant patients with APS should be centralised in academic centres and close cooperation between obstetricians and internal medicine is necessary.