Preeclampsia: the clinical syndrome

Preeclampsia is the most common hypertensive disease of pregnancy, affecting 5-8% of pregnancies (Saftlas et al., 1990) and accounting for nearly 18% of maternal deaths (ACOG, 2002) in the United States. Little change has been noted in the incidence of this disease in the United States during the national data-collection periods of 19931997 and 2001-2005 (Berg et al., 2009). Preeclampsia is also associated with adverse fetal outcomes, including intrauterine growth retardation (IUGR), placental abruption, oligohydramnios and non-reassuring fetal surveillance. It is clinically defined as hypertension and proteinuria with onset following the 20th week of pregnancy (Wagner, 2001). Preeclampsia can be further differentiated into mild and severe forms. Mild preeclampsia is defined by a systolic blood pressure of >140 mmHg or a diastolic blood pressure >90 mmHg in combination with 300 mg of proteinuria over 24 hours. Blood pressure elevations must be confirmed via two separate measurements taken at least 6 hours apart. Severe preeclampsia is diagnosed if there are more severe elevations of blood pressure or evidence of other endorgan dysfunction. The specific criteria as defined by the American Congress of Obstetricians and Gynecologists (ACOG) are shown in Box 1. Patients with severe preeclampsia can also exhibit hemoconcentration due to intravascular volume depletion and elevated serum uric acid levels (Wagner, 2001). HELLP syndrome is a specific variant of severe preeclampsia. HELLP is an acronym for hemolysis, elevated liver enzymes and low platelets. It has been suggested that, to meet the criteria for HELLP syndrome, a patient’s test results must indicate: microangiopathic anemia on a peripheral smear; liver aspartate aminotransferase (AST) levels >70; lactate dehydrogenase (LDH) levels >600 or total bilirubin >1.2 (indicative of significant hemolysis); and a platelet count <100,000 (Sibai, 2004). Other recommendations are less stringent and recognize the diagnosis of partial HELLP syndrome when some of the above characteristics are absent. The multiple criteria for the diagnosis of severe preeclampsia illustrate the multifocal nature of the disease. Elevated proteinuria and oliguria are indicative of renal dysfunction. Headache and visual changes are evidence of central nervous system involvement. Impaired liver dysfunction is typically defined as liver function tests [AST or alanine aminotransferase (ALT) levels] that exceed twice the upper limit of normal (ACOG, 2002). Fetal growth restriction is variously defined as an estimated fetal weight of less than the 10th, 5th or 3rd percentile (Figueras and Gardosi, 2011). Management of preeclampsia consists of two options: delivery or observation. Management decisions depend on the gestational age at which preeclampsia is diagnosed. The only effective treatment for preeclampsia is delivery of the fetus and placenta, and the decision to deliver involves