MULTIFREQUENCY INFRADIAN VARIATION OF BLOOD-PRESSURE DURING AND AFTERHUMAN-PREGNANCY

We used a chronobiologic approach to explore the possibility that ther e may be similar to 7-day (circaseptan) and -30-day (circatrigintan) c omponents in blood pressure during a healthy human pregnancy, the amen orrhea of this status notwithstanding. The results were compared with those obtained from data longitudinally monitored on the same subject at a time when she was not pregnant. The woman under study used an ABP M-630 Colin (Komaki, Japan) device to monitor her blood pressures and heart rates at half to 1-h intervals, with few interruptions. During p regnancy, starting during the first gestational week, she monitored he rself for 2 of each 6-day span for the entire duration of pregnancy (a total of 76 days of monitoring). Additionally, with a monitoring prot ocol similar to that during pregnancy, the subject used the same blood pressure monitor for a total of 78 days during 9.6 months and startin g 1 year after delivery. The data obtained oscillometrically for both longitudinal profiles were analyzed separately by multiple-component l inear least-squares rhythmometry, a procedure used to describe the per iodic waveform of nonsinusoidal rhythms. The analysis of blood pressur e variability during pregnancy allows the identification not only of t he circadian (with a period of 24 h), but also of other statistically significant components with periods of 156 (6.5 days, apparently free- running from the social week) and of 720 h (30 days) for both systolic and diastolic blood pressure. This multiharmonic time structure is so mewhat different during menstruation in the same woman and during a si milar time span, with statistically significant components of 96 h (4 days), 192 h (8 days), and 960 h (40 days) for both systolic and diast olic blood pressure. Moreover, the ratio between the amplitudes of the infradian components identified during pregnancy in clinical health i s reversed from that obtained in women with preeclampsia. The complex time-structure of blood pressure during pregnancy offers new endpoints to be taken into account for an early identification of gestational h ypertension or even preeclampsia.