Circadian rhythm of blood pressure and heart rate in uncomplicated healthy human pregnancy

Blood pressure (BP) and heart rate (HR) were automatically monitored for 48 hours at 15-min intervals in 31 hospitalized pregnant women at low risk for BP disorder. Each of the recorded 56 data series for systolic arterial pressure (SAP), diastolic arterial pressure (DAP) and heart rate (HR) was chronobiologically assessed. A rhythm-adjusted mean (MESOR), 24-hour and harmonic amplitudes, 24-hour and harmonic acrophases were grouped by trimester of pregnancy and further subjected to analysis of variance. The repeatedly reported well-established lowering of BP MESOR was not detected in this particular sample, while, as anticipated, the HR MESOR increased statistically significantly in the course of pregnancy. Ultradian components, with a period from 1 to 12 hours and an amplitude higher than that of the 24-hour component, were found in 25% of the SAP data series recorded during the second and third trimesters. Such ultradian components were detected in only one of the 36 simultaneously recorded HR series. Analysis of the individual variability in the statistical endpoints, based on 9 women contributing records in each trimester of pregnancy, revealed in the course of pregnancy greater variability in circadian amplitude and acrophase than in the individual BP MESOR. Healthy pregnancy differentially affects the BP and HR chronomes. The reproducible individual BP MESOR, obtained by 48-hour monitoring at 15-min intervals in hospitalized pregnant women, may be useful in early diagnosis of gestational hypertension, but for detection of circadian hyper-amplitude-tension (CHAT), longer than 48-hour monitoring is needed.