Is a Threshold Increase in Blood Pressure Predictive of Preeclampsia? a Prospective Cohort Study

Abstract

Eight-hundred and eight nulliparous women were prospectively studied to determine whether increments in blood pressure from values obtained earlier in pregnancy were predictive of preeclampsia. Blood pressure was recorded at monthly intervals. The monthly blood pressure reading which was used as the baseline for comparisons was varied in order to determine if there was a critical period from which increments would be most predictive of preeclampsia. The rate of occurrence of systolic (20 or 30 mm Hg) and of diastolic (10 or 15 mm Hg) increments from each reference period was determined among women who remained normotensive (n=707) and among women who later developed preeclampsia (n=44). Systolic (20 and 30 mm Hg) and diastolic (10 and 15 mm Hg) blood pressure increments were significantly more prevalent among women with future preeclampsia. However, these increments displayed a poor sensitivity (7–55%) for the detection of future preeclampsia and a variable specificity (69 to 99%). The positive predictive values were also low (7–42%). Thus the evaluation of incremental changes in blood pressure, in out-patient pregnant women, is not a useful method of screening for impending preeclampsia.