Background and objective: Changes in circadian variation of blood pressure could be used either to predict preeclampsia or to assess its severity. With the objective of identifying potential differences in blood pressure at the early stages of pregnancy, we examined and compared the characteristics of circadian variability in blood pressure in healthy and complicated pregnant women who were systematically monitored throughout gestation.
Subjects and method: We analyzed 2,014 blood pressure series sampled through ambulatory monitoring for 48 hours once every 4 weeks from the first obstetric visit until delivery. The study included 205 women with uncomplicated pregnancy, 92 with gestational hypertension and 31 with preeclampsia. The circadian pattern of blood pressure variation for each group and trimester of gestation was established by means of a population multiple-components analysis.
Results: Differences in the 24-hour mean between healthy and complicated pregnancies were highly significant in all trimesters (p < 0.001), with values of 15.1 and 9.1 mmHg for systolic and diastolic blood presure, respectively, in the third trimester of pregnancy. The 24-hour mean of systolic/diastolic blood pressure for complicated pregnancies was always below 120/72 mmHg. Results further indicated similar circadian characteristics between gestational hypertension and preeclampsia in the first trimester of pregnancy. The difference between these two groups in the 24-hour mean was significant in the second trimester for systolic (3 mmHg; p = 0.002) but not diastolic blood pressure (0.9 mmHg; p = 0.230). In the third trimester, the difference between gestational hypertension and preeclampsia was significant for both variables (5.4 and 3.7 mmHg for systolic and diastolic blood pressure, respectively; p < 0.001).
Conclusions: The differences in blood pressure between healthy and complicated pregnancies, which are observed as early as the first trimester of pregnancy, are detected when both systolic and diastolic blood pressure measurements in women with a late diagnosis of gestational hypertension or preeclampsia fall within accepted ranges of normotension. These differences offer new end points that may lead to an early identification of hypertensive complications in pregnancy as well as to the establishment of prophylactic interventions.