Pre-eclampsia is a multisystem disorder that usually manifests clinically as hypertension and proteinuria. It is a disease exclusive to pregnancy, and remains a leading cause of maternal and fetal morbidity and mortality. Every year in Norway 4,5% of pregnant women is affected. The condition is hard to predict. Sometimes it develops slowly. Sometimes it develps to a life-threatening situation for both mother and child in just a few hours. The most feared complications are eclampsia and HELLP-syndrome. Despite extensive research, the mechanisms that cause pre-eclampsia are unknown, and it has been considered to be the ”disease of theories”. The trigger seems to originate in the uteroplacental bed due to defect trophoblst invasion and placental ischaemia. What causes this ineffective invasion is not understood yet. The aim of treatment is to protect the mother and fetus from the consequences of hypertension and to prolong the pregnancy to avoid the problems of prematurity.