24-hour blood pressure monitoring to evaluate the effects of nifedipine in pre-eclampsia and in chronic hypertension in pregnancy.

OBJECTIVE: To investigate the effect of 7 to 14 days of therapy with nifedipine (sustained-release preparation) on the 24-hour blood pressure patterns of pregnant women with pre-eclampsia or chronic hypertension, and to test the utility of blood pressure monitoring in modulating the timing and dosage of the drug. DESIGN: 24-hour automatic blood pressure monitoring of pregnant women with pre-eclampsia or chronic hypertension before and after nifedipine treatment. SETTING: Centre for Prevention, Diagnosis and Treatment of Hypertension in Pregnancy, University of Turin, Italy. POPULATION: Sixteen pregnant women with pre-eclampsia and 17 with chronic hypertension. METHODS: 24-hour blood pressure monitoring was performed before the beginning of the therapy and after 7 to 14 days of treatment with sustained-release nifedipine. MAIN OUTCOME MEASURES: Chronobiological analysis of systolic and diastolic blood pressure values was performed; MESOR, amplitude, acrophase, hyperbaric index, percent time elevation and significance of rhythm were calculated before and after treatment. RESULTS: 6336 blood pressure measurements were analysed. Systolic and diastolic MESOR values were significantly decreased after nifedipine treatment both in pre-eclampsia and in chronic hypertension. However, the antihypertensive effect of nifedipine in pre-eclampsia was especially pronounced during evening and night, while in chronic hypertension it was more constant during the 24-hour period. 24-hour blood pressure monitoring allowed adjustment, when necessary, to the timing and dosage of nifedipine in accordance with the blood pressure patterns of each patient, using the hyperbaric index and percent time elevation as objective parameters for the evaluation of treatment efficacy. CONCLUSIONS: 24-hour blood pressure monitoring is a good method to optimise treatment, and confirms that nifedipine is useful for the control of maternal blood pressure in pregnancy.