Reminders about physiology:
During pregnancy, kidney perfusion as well as glomerular function increases from 30% to 50%. The systolic and diastolic arterial blood pressures normally fall around 10 to 15 mmHg, when compared to the values preceding the pregnancy. The vasodilatation in the uterus, the kidneys and the skin, as well as the release of vasodilatating prostaglandins and a reduced arteriolar sensibility to angiotensin II play a role in the sinking of blood pressure during pregnancy.
In the third trimester the arterial diastolic blood pressure should not exceed 85 mmHg.
The rise of the arterial blood pressure in the course of a pregnancy is nevertheless a common complication and is potentially dangerous. A blood pressure that exceeds 140/90 mmHg is pathological.
Eclampsia: pathogenic mechanisms
The pathogenesis of this disease is still unclear. The lesion that lies at its base seems to be a utero-placental ischaemia.
Various circumstances that promote it can be mentioned, namely the over-stretching of the uterus in the case of a twin pregnancy, vessel lesions in connection with diabetes, or a villus hypoxia. Coagulopathies and the hormonal factors causing them, possibly also immunologic processes, are also thought to be responsible.