Circadian blood pressure variability in healthy pregnancy and women with gestational hypertension

Conventional time-unspecified single measurements of blood pressure and heart rate may be misleading since they may be influenced, among other factors, by the patient´s emotional state, position and diet, and by external stimuli. The evaluation of predictable variability in blood pressure and heart rate by (1) the use of fully ambulatory devices, and (2) the proper processing of the time series thus obtained, can be useful in assessing early cardiovascular disease risk in pregnancy. We have used this approach to examine characteristics of blood pressure variability during pregnancy with a view of an early recognition of blood pressure elevation. A total of 193 pregnant women provided 301 profiles of blood pressure sampled mostly hourly for about 48 hours with an ambulatory device. Circadian parameters of blood pressure were first computed for each single profile of measurement by the least-squares fit of a 24-hour cosine curve, and then used for assessing circadian rhythm characteristics for each group of subjects (complicated vs. uncomplicated) in each trimester of pregnancy. Results indicate that, on a group basis, as compared to uncomplicated pregnancies, a statistically significant elevation of blood pressure is found in pregnancies with gestational hypertension or preeclampsia in all trimesters. These differences occur with values for systolic and diastolic blood pressure well within the currently accepted range of physiological variation. These results provide sensitive parameters for use in early risk assessment and as a guide to preventive intervention during pregnancy