High blood pressure during pregnancy (BP > or = 140/90 mmHg) is sometimes already noted before conception, with usually a good prognosis (although it could predispose to preeclampsia). alpha-methyldopa is the best treatment when needed (agents blocking the renin angiotensin system are not recommended). Preeclampsia, a form of hypertension noted after 20 weeks of gestation with proteinuria is a more serious condition (BP > or = 140/90 mmHg or increase in BP from the 1st trimester > or = 25/15 mmHg). It is generated by placental ischemia and creates maternal endothelial lesions which in turn decrease the blood flow to placenta leading to maternal and fetal syndromes. Hospitalisation is mandatory. No measure other than delivery is known to attenuate or reverse its progression. Treating hypertension during pregnancy (when blood pressure > or = 170/110 mmHg) aims at preventing maternal risk (stroke or eclampsia) but has few effect on foetal lesions. Prevention of this syndrome, which represents the first secondary cause of hypertension, is until now disappointing.