Paroxysmal nocturnal haemoglobinuria (PNH) is a rare, acquired, intrinsic haemolytic anaemia believed to occur with an incidence of 1.5 per million in France. The disease is characterised by acute and chronic intravenous haemolysis and pancytopenia, without leukocytopenia. Pregnancy is rare and a high incidence of spontaneous abortion has been reported. The case reported here describes the successful outcome of a pregnancy where PNH was diagnosed. A 25 year old primigravida was admitted for evaluation of pancytopenia discovered in the 32nd week of an hypertensive pregnancy. On admittance R.B.C. were 1.67 x 10(12)/1, W.B.C. 3.4 x 10(9)/1 and platelets 12 x 10(9)/1; Hb was 6.8 g/dl and MGV 126 mu 3. Initial arterial pressure was 160/90 mm/Hg, with oedema and proteinuria 0.7 g per day. Obstetrical parameters were good and physical examination revealed to spontaneous haemorrhage, no jaundice, no dark urine, no organomegaly, no consumptive coagulopathy (C.C.) and no biological liver abnormalities. The patient received saline-washed packed red cells and fresh platelets. R.B.C. increased to 2.5 x 10(12)/1 and remained stable and platelets decreased to 5 x 10(9)/1 with increased arterial pressure and proteinuria, and appearance of C.C. A Caesarean section was performed, under general anaesthesia, and a male healthy baby weighing 2750 g was delivered. The post operative course was uneventful, except for a parietal haematoma which needed surgical evacuation. Because of the low platelet count, no heparin was given and the patient had no thrombosis and no infection.(ABSTRACT TRUNCATED AT 250 WORDS)