Pathophysiology

Hypertension with superimposed preeclampsia

Chronic hypertension exists when the blood pressure is 140/90 or higher before pregnancy or before the 20th week of gestation or persists 42 days following childbirth.  If the diastolic blood pressure is greater than 80 mm Hg during the second trimester, chronic hypertension should be suspected.  
Preeclampsia, a syndrome the affects both mother and fetus, is clinically defined as an increase in blood pressure after 20 weeks gestation accompanied by proteinuria.  
Symptoms of preeclampsia include the failure of the uterine spiral arteries to transform from thick-walled muscular vessels to saclike flaccid vessels, exaggerated inflammatory response, and inappropriate endothelial-cell activation.  Characteristics of preeclampsia include maternal vasospasm resulting in decreased perfusion to virtually all organs, including the placenta, a decrease in plasma volume, activation of the coagulation cascade, and alterations in glomerular capillary endothelium.  The increased platelet activation and markers of endothelial activation can predate clinically evident preeclampsia by weeks or even months.  Preeclampsia develops in approximately 25% of women previously found to have chronic hypertension.  

Davidson, M.R., London, M.L. & Ladewig, W.P. (2008). Old’s Maternal-newborn nursing and women’s health across the lifespan (8th ed.) Upper Saddle River, NJ: Prentice-Hall.