he systolic and diastolic blood pressure levels of 140/90 mm Hg have been arbitrarily used since the 1950s to define "hypertension" in nonpregnant individuals. However, these levels were selected by insurance companies to characterize a group of middle-aged men. It seems more realistic to deine normalrange blood pressures that fall between an upper and lower limit for a particular population-such as young, healthy, pregnant women. A schematic example using arbitrary mean arterial blood pressure readings is shown in Figure 40-1. Data curves for both women show blood pressure measurements near the ...Patient A ...Patient B )..:J,
C,
FIGURE 40-1 Schematic shows normal reference ranges for mean arterial blood pressure changes across pregnancy. Patient A (blue) has mean blood pressures near the 20th percentile throughout pregnancy. Patient B (red) has a similar pattern with mean pressures at the 25th percentile until approximately 36 weeks when her blood pressure begins to rise. By term, it is substantively higher and in the 75th percentile, but she is still considered "normotensive." 25th percentile until 32 weeks. These begin to rise in patient B, who by term has substantively higher blood pressures. However, her pressures are still < 140/90 mm Hg, and thus she is considered to be "normotensive." We use the term delta hypertension to describe this rather acute rise in blood pressure. Some of these women will go on to have obvious preeclampsia, and some even develop eclamptic seizures or HELLP (hemolysis, devatedliver enzyme levels, low 2latelet count) syndrome while still normotensive.
his diagnosis is made in women whose blood pressures reach 140/90 mm Hg or greater for the irst time after midpregnancy, but in whom proteinuria is not identiie. Almost half of these women subsequently develop preeclampsia syndrome. Even so, when blood pressure increases appreciably, it is dangerous to both mother and fetus to ignore this rise only because proteinuria has not yet developed. As Chesley (1985) emphasized, 10 percent of eclamptic seizures develop before overt proteinuria can be detected. Finally, gestational hypertension is reclassiied by some as transient hypertension if evidence for preeclampsia does not develop and the blood pressure returns to normal by 12 weeks postpartum.
Preeclampsia is best described as a pregnancy-speciic syndrome that can aect virtualy evey organ system. In addition, it heralds a higher incidence of cardiovascular disease later in life (p. 744). Although preeclampsia is much more than simply gestational hypertension with proteinuria, appearance ofproteinuria remains an important diagnostic criterion. Thus, proteinuria is an objective marker and relects the system-wide endothelial leak that characterizes the preeclampsia syndrome.
In some women with the preeclampsia syndrome, neither overt proteinuria nor fetal-growth restriction are features (Sibai, 2009). Because of this, the Task Force (2013) suggests other diagnostic criteria, which are shown in Table
Evidence of multiorgan involvement may include thrombocytopenia, renal dysfunction, hepatocellular necrosis, central nervous system perturbations, or pulmonary edema.
• Indicators of Preeclampsia Severity