Predictable blood pressure variability in healthy and complicated pregnancies

With the aim of describing the predictable pattern of blood pressure (BP) v ariability during gestation, we analyzed 2430 BP series systematically samp led by ambulatory monitoring for 48 consecutive hours every 4 weeks from th e first obstetric visit (usually within the first trimester of pregnancy) u ntil delivery in 235 normotensive women, 128 women who developed gestationa l hypertension, and 40 women who had a final diagnosis of preeclampsia. The pattern of variation along gestation of the 24-hour means of BP and heart rate was established for each group of women by polynomial regression analy sis. For normotensive women, results indicate a steady decrease in BP up to 20 weeks of pregnancy, followed by an increase in BP up to the day of deli very, with an average 8% BP increase between the middle of gestation and de livery. In complicated pregnancies, BP is stable until the 22nd week of ges tation and then increases linearly for the remainder of the pregnancy. Comp licated pregnancies are characterized by a 9% and 13% increase in systolic and diastolic Bps, respectively, during the second half of gestation. Resul ts also indicate that during the first half of pregnancy, systolic but not diastolic BP is slightly elevated in women who developed preeclampsia compa red with those who developed gestational hypertension. During the second ha lf of gestation, the linear trend of increasing BP for women who developed preeclampsia has a significantly higher slope than the trend for women with gestational hypertension. For both healthy and complicated pregnancies, he art rate increases until the end of the second trimester and slightly decre ases thereafter. This study of women systematically sampled by 48-hour ambu latory BP monitoring throughout gestation confirms the predictable pregnanc y-associated variability in BP and provides proper information for the esta blishment of reference limits for BP to be used in the early diagnosis of h ypertensive complications in pregnancy. Those limits should be developed as a function of gestational age, taking into account the trends in BP throug hout pregnancy demonstrated here.