Hypertensive disorders of pregnancy.

The National High Blood Pressure Education Program Working Group on High Blood Pressure in Pregnancy has defined four categories of hypertension in pregnancy: chronic hypertension, gestational hypertension, preeclampsia, and preeclampsia superimposed on chronic hypertension. A maternal blood pressure measurement of 140/90 mm Hg or greater on two occasions before 20 weeks of gestation indicates chronic hypertension. Pharmacologic treatment is needed to prevent maternal end-organ damage from severely elevated blood pressure (150 to 180/100 to 110 mm Hg); treatment of mild to moderate chronic hypertension does not improve neonatal outcomes or prevent superimposed preeclampsia. Gestational hypertension is a provisional diagnosis for women with new-onset, nonproteinuric hypertension after 20 weeks of gestation; many of these women are eventually diagnosed with preeclampsia or chronic hypertension. Preeclampsia is the development of new-onset hypertension with proteinuria after 20 weeks of gestation. Adverse pregnancy outcomes related to severe preeclampsia are caused primarily by the need for preterm delivery. HELLP (i.e., hemolysis, elevated liver enzymes, and low platelet count) syndrome is a form of severe preeclampsia with high rates of neonatal and maternal morbidity. Magnesium sulfate is the drug of choice to prevent and treat eclampsia. The use of magnesium sulfate for seizure prophylaxis in women with mild preeclampsia is controversial because of the low incidence of seizures in this population.