Laboratory abnormalities in pregnancy-associated hypertension: Frequency and association with pregnancy outcomes

OBJECTIVE: To estimate the frequency of abnormal laboratory test results in pregnancy-associated hypertension and the relationship with pregnancy outcomes. METHODS: This was a secondary analysis of a multicenter trial of Vitamin C and E for prevention of pregnancy-associated hypertension in low-risk nulliparous women. Laboratory abnormalities included: platelets less than 100,000/mm³, aspartate aminotransferase 100 units/L or greater, creatinine 1.5 mg/dL or greater, lactate dehydrogenase 600 units/L or greater, total bilirubin 1.2 mg/dL or greater, or evidence of hemolysis on peripheral smear. Mild pregnancy-associated hypertension was defined as blood pressure 140-159/90-109 mm Hg. Severe pregnancy-associated hypertension was defined as persistent blood pressure 160/110 mm Hg or greater, acute antihypertensive treatment, or any blood pressure elevation associated with clinical signs of end-organ dysfunction (one or more of headache, epigastric pain, blurred vision, pulmonary edema, eclampsia, or oliguria). Pregnancy outcomes were compared across four groups: I, mild hypertension alone; II, mild hypertension+abnormal laboratory values; III, severe pregnancy-associated hypertension alone; and IV, severe pregnancy-associated hypertension+abnormal laboratory values. RESULTS: Of 9,969 women, 2,752 (27.9%) developed pregnancy-associated hypertension and of these, laboratory abnormalities occurred in 7.3%. Laboratory abnormalities increased with severity of hypertension: mild hypertension alone (4.9%), severe hypertension alone (8.9%), and mild or severe hypertension with clinical signs of end-organ dysfunction (12.2%) (P for trend<.001). Compared with women with mild hypertension alone, the adjusted odds for the perinatal composite (2-fold to 4.8-fold in Category III-IV), preterm birth (2.1-fold to 7.8-fold in Category II-IV), and other adverse perinatal outcomes increase with disease severity, particularly with laboratory abnormalities and severe clinical signs. CONCLUSION: The frequency of abnormal laboratory values in women with pregnancy-associated hypertension increases with disease severity. Adverse perinatal outcomes increase in the presence of abnormal laboratory values, particularly in those with clinical signs, likely atttributable in part to the decision to deliver early.