SummaryIn a woman with a placenta praevia marginalis delivery was complicated 1°by an acute hemorrhagic disorder with disappearance of the fibrinogen from the plasma; 2°by acute renal insufficiency.The authors discuss the pathogenic parenthood of those complications. The following hypothesis is formulated : the fibrinogen is deposited as fibrin in the smaller arteries of the kidney leading to different forms of symmetric necrosis of the renal cortex.