The cause(s) of hypertensive pregnancy is uncertain and include immune, genetic, and placental abnormalities. All may contribute to endothelial dysfunction characteristic of preeclampsia. Endothelial dysfunction may, in turn, underlie several critical features of preeclampsia, including vaso- constriction, hypertension, loss of the usual pregnancy- associated refractoriness to pressor effects of angiotensin II, increased platelet aggregation, and proteinuria (1).