Objective: To investigate whether a chronobiological analysis applied to automated 24-hour blood pressure monitoring in early pregnancy provides objective parameters enabling detection of single patients at risk of pregnancy-induced hypertension or preeclampsia.
Methods: 24-hour automatic blood pressure monitoring was performed at 8-16 and 20-25 gestational weeks in 104 women at risk of pregnancy-induced hypertension or preeclampsia. The subjects were hospitalized to be synchronized to rest-activity and meal-timing schedules. All women were followed longitudinally until post-partum. Chronobiological analysis of blood pressure values was performed; sensitivity, specificity and predictive values of MESOR and hyperbaric index were also calculated. Incidence of pregnancy-induced hypertension or preeclampsia, gestational week at delivery and birthweight were recorded.
Results: Nine thousand nine hundred and eighty-four blood pressure measurements were analyzed. In patients who later developed overt hypertension, systolic and diastolic blood pressure MESOR, hyperbaric index and percent time elevation were already significantly higher in early pregnancy than in those who remained normotensive. The best sensitivity and specificity was obtained between 20-25 weeks of gestation with systolic single cosinor MESOR and Hyperbaric Index using as cut-off 103 mmHg (sensitivity: 88%; specificity: 75%) and 10 mmHg/24 hour (sensitivity: 70%; specificity: 92%), respectively.
Conclusions: The chronobiological analysis applied to 24-hour blood pressure monitoring during pregnancy allows definition of objective cut-off values which can be particularly useful in the routine clinical practice when the risk of developing pregnancy-induced hypertension or preeclampsia must be calculated in the individual subject.