The concept that endothelial cell activation and injury constitutes the key pathogenetic event is receiving increasing support, but the causative factor or factors are, as yet, unclear. The search for a reliable and clinically useful test to identify pregnant women at risk continues. No definitive conclusions can yet be drawn as to the efficacy and safety of low-dose aspirin prophylaxis. Monitoring of maternal-fetal condition, careful consideration of maternal and perinatal risks, and a balanced decision to continue or terminate pregnancy are key elements of clinical management.