Variability of blood pressure in normal and abnormal pregnancy.

Using an automatic indirect method of measurement, diurnal blood pressure patterns have been studied in normal and hypertensive pregnancies. In the last trimester, normotensive and hypertensive pregnant subjects show small but significant increases of blood pressure that develop especially during the evening and night. This change is more clear-cut for the systolic than the diastolic pressure. The tendency to a relatively greater increased pressure at night is exaggerated in preeclampsia. This fact explains earlier observations of a dimunution of the nocturnal fall of blood pressure in preeclampsia. In very severe preeclampsia, the nocturnal increase of blood pressure may be so exaggerated as to reverse the normal diurnal blood pressure pattern. These changes have been documented sequentially, and their implications are discussed briefly.