Multifrequency infradian variation of blood pressure during and after human pregnancy

We used a chronobiologic approach to explore the possibility that there may be similar to 7-day (circaseptan) and -30-day (circatrigintan) components in blood pressure during a healthy human pregnancy, the amenorrhea 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 ABPM-630 Colin (Komaki, Japan) device to monitor her blood pressures and heart rates at half to 1-h intervals, with few interruptions. During pregnancy, starting during the first gestational week, she monitored herself for 2 of each 6-day span for the entire duration of pregnancy (a total of 76 days of monitoring). Additionally, with a monitoring protocol similar to that during pregnancy, the subject used the same blood pressure monitor for a total of 78 days during 9.6 months and starting 1 year after delivery. The data obtained oscillometrically for both longitudinal profiles were analyzed separately by multiple-component linear least-squares rhythmometry, a procedure used to describe the periodic waveform of nonsinusoidal rhythms. The analysis of blood pressure variability during pregnancy allows the identification not only of the 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 somewhat different during menstruation in the same woman and during a similar time span, with statistically significant components of 96 h (4 days), 192 h (8 days), and 960 h (40 days) for both systolic and diastolic blood pressure. Moreover, the ratio between the amplitudes of the infradian components identified during pregnancy in clinical health is 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 hypertension or even preeclampsia.