Women who have or develop high blood pressure during pregnancy are all at increased risk of complications antenatally, intrapartum and in the puerperium. The increased risk applies to the mother as well to the fetus. Preeclampsia is the most serious form of hypertensive pregnancy complications. Preeclampsia is, however, not primarily a hypertensive disease but a disorder induced by factors dependent on the presence of placenta. The prime target of the placenta dependent factors is the vascular endothelium. Therefore the complications are associated with the vascular system, i.e. intravascular coagulation, bleeding and organ failure following poor perfusion. The fetus is at increased risk due to growth retardation and hypoxia following placental damage. Treatment of the hypertension is first indicated if the blood pressure rises to a level of increased risk of cerebral vascular complications, i.e. above 105-110 mmHg. Delivery is the only causal treatment and is always indicated if severe maternal or fetal complications develop.