Altered interactions of heart rate and blood pressure during normal and abnormal pregnancy

The assessment of the autonomic cardiovascular regulation provides important diagnostic and prognostic information. The aim of this study was to investigate the alterations of this autonomic regulation in the progress of a normal pregnancy and in several pregnancy disorders associated with hypertension, especially pre-eclampsia, applying the method of Joint Symbolic Dynamics (JSD). The JSD reveals nonlinear interactions/ coupling between two time series. Continuous, non-invasive 30 min blood pressure recordings from women with normal pregnancies (CON), with chronic hypertension (CH), with pregnancy-induced hypertension (PIH) and with pre-eclampsia (PE) were analyzed. It could be shown that the cardiovascular regulation system was changed considerably between a first and a second part of gestation in normal pregnancy. These changes were revealed by the analysis of the interactions of heart rate and blood pressure applying the bivariate method JSD. Further on, significant changes of these interactions led to a significant differentiation between normal pregnancy and pre-eclampsia and between chronic or pregnancy-induced hypertension and pre-eclampsia. The JSD provides new information about interaction and coupling between heart rate and blood pressure, increases the ability to diagnose pathological changes and finally may assist the physician to avoid serious maternal and prenatal complications.