Pathophysiology of pregnancy-induced hypertension

Pregnancy-induced hypertension (PIH) is estimated to affect 7% to 10% of all pregnancies in the United States. Despite being the leading cause of maternal death and a major contributor of maternal and perinatal morbidity, the mechanisms responsible for the pathogenesis of PIH have not yet been fully elucidated. Studies during the past decade, however, have provided a better understanding of the potential mechanisms responsible for the pathogenesis of PIH. The initiating event in PIH appears to be reduced uteroplacental perfusion as a result of abnormal cytotrophoblast invasion of spiral arterioles. Placental ischemia is thought to lead to widespread activation/dysfunction of the maternal vascular endothelium that results in enhanced formation of endothelin and thromboxane, increased vascular sensitivity to angiotensin II, and decreased formation of vasodilators such as nitric oxide and prostacyclin. The quantitative importance of the various endothelial and humoral factors in mediating the reduction in renal hemodynamic and excretory function and elevation in arterial pressure during PIH is still unclear. Investigators are also attempting to elucidate the placental factors that are responsible for mediating activation/dysfunction of the maternal vascular endothelium. Microarray analysis of genes within the ischemic placenta should provide new insights into the link between placental ischemia and hypertension. More effective strategies for the prevention of preeclampsia should be forthcoming once the underlying pathophysiologic mechanisms that are involved in PIH are completely understood.