Circadian blood pressure variability as a function of parity in normotensive pregnant women.

Studies based on office blood pressure measurements concluded that parity has significant effects on blood pressure during pregnancy. The authors evaluated possible differences in the circadian pattern of blood pressure as a function of parity in normotensive women systematically studied by ambulatory blood pressure monitoring. They analyzed 1400 blood pressure series sampled for 48 consecutive hours every 4 weeks from the first obstetric visit (usually within the first trimester of pregnancy) until delivery in 234 women. The circadian pattern of blood pressure variation for each group (nulliparous vs. multiparous) and trimester of gestation was established by population multiple-component analysis. A highly statistically significant circadian pattern, described by a model that includes components with periods of 24 and 12 hours, was demonstrated for systolic and diastolic blood pressure for both groups of pregnant women in all trimesters (p<0.001). There was no significant difference in 24-hour mean among groups divided by parity at any stage of pregnancy (p>0.315). Data obtained from systematic ambulatory monitoring in normotensive pregnant women indicate the lack of differences in blood pressure according to parity. Reference thresholds for blood pressure in pregnancy could thus be developed as a function of rest-activity cycle and gestational age only, independent of parity.