Platelet activation in the hypertensive disorders of pregnancy.

The hypertensive disorders of pregnancy, including gestational hypertension, pre-eclampsia and eclampsia, continue to be an important cause of maternal morbidity and mortality. Abnormal placentation is considered to be the main instigating factor, which then leads to widespread maternal endothelial activation and dysfunction. This endothelial perturbation leads to the release of many substances into the circulation, many of which result in platelet activation. For example, there is an imbalance between the levels of prostacyclin (a vasodilator and platelet inhibitor) and thromboxane (a platelet activator and vasoconstrictor), which then results in the maintenance of high blood pressure and complications. It is also likely that platelets play an important part in the pathogenesis of hypertension in pregnancy. The use of antiplatelet drugs has been shown to be effective in reducing the incidence of gestational hypertension in women at high risk and in preventing the complications associated with it. In addition, some antihypertensive agents are effective in reversing platelet activation in essential hypertension and, therefore, their use in pregnancy-induced hypertension may be beneficial in more ways than simply blood pressure reduction.