Diagram of the placenta and its position in the uterus during pregnancy The presence of a placenta is required, and<unk>  resolves if it is removed. Reduced blood flow to the placenta (placental hypoperfusion) is a key feature of the process. It is accompanied by increased sensitivity of the maternal vasculature to agents which cause constriction of the small arteries, leading to reduced blood flow to multiple organs. Vascular dysfunction-associated maternal conditions such as Lupus, hypertension, and renal disease, or obstetric conditions that increase placental volume without an increase in placental blood flow (such as twin pregnancy) can increase risk for pre-eclampsia. Also, an activation of the coagulation cascade may lead to microthrombi formation, which can further impair blood flow. Thirdly, increased vascular permeability results in the shift of extracellular fluid from the blood to the interstitial space, with further reduction in blood flow, and edema. These events lead to hypertension; renal, pulmonary, and hepatic dysfunction; and cerebral edema with cerebral dysfunction and convulsions. Before symptoms appear, increased platelet and endothelial activation may be detected. Placental hypoperfusion is linked to abnormal modelling of the fetal–maternal placental interface that may be immunologically mediated. The pathogenesis of pre-eclampsia is poorly understood, but it likely is attributed to factors related to the mother and placenta, because pre-eclampsia is seen in molar pregnancies absent of a fetus or fetal tissue. The placenta produces the potent vasodilator adrenomedullin: it is reduced in pre-eclampsia and<unk> . Other vasodilators are also reduced, including prostacyclin, thromboxane A2, nitric oxide, and endothelins, also leading to vasoconstriction.<unk>  is a form of hypertensive encephalopathy: cerebral vascular resistance is reduced, leading to increased blood flow to the brain, cerebral edema and resultant convulsions. An eclamptic convulsion usually does not cause chronic brain damage unless intracranial haemorrhage occurs.
Eclampsia
Pre-eclampsia
Hypertensive disease of pregnancy
Hyperemesis gravidarum
Early pregnancy bleeding
Gestational hypertension
Antepartum bleeding
Recurrent miscarriage