The circadian rhythm of blood pressure during pregnancy.

OBJECTIVE To review the literature on the circadian rhythm of blood pressure during pregnancy. DATA SOURCES Computerized searches on MEDLINE, CINAHL, and MIRLYN. STUDY SELECTION Selected studies from 1 969 to 1997 were evaluated. DATA EXTRACTION Data were extracted and information was organized under the following areas: definition of and the interconnection between circadian rhythm and blood pressure; the circadian variability of blood pressure throughout the trimesters; the patterns of the circadian rhythm of blood pressure in pregnancies defined as normal and those complicated by chronic hypertension and preeclampsia; and clinical implications. DATA SYNTHESIS The circadian rhythm of blood pressure in pregnancy is the same as in the non-pregnant state, with a nocturnal decrease, especially during sleep. In patients with chronic hypertension, the nocturnal fall in blood pressure may be steeper. Patients with mild preeclampsia may experience a less pronounced nocturnal decrease in blood pressure. Patients with severe preeclampsia may display a reversed circadian rhythm, with no decrease and/or an increase in nocturnal blood pressure. CONCLUSIONS The patterns of the circadian rhythm of blood pressure during normal pregnancy and pregnancies complicated by chronic hypertension and preeclampsia warrant consideration when monitoring patients and implementing management plans.