Chronic Hypertension: Effect of Blood Pressure Control on Pregnancy Outcome

摘要

Chronic hypertension (cHTN) complicates 1% to 2% of pregnancies. In these pregnancies, there is a 10-fold increase in the risk of preeclampsia (PE) and 2-fold increase in risk of small for gestational age (SGA) neonates. The current recommendation for patients with cHTN is that severe hypertension should be controlled to reduce the risk of maternal death and morbidity, but in the case of mild to moderate hypertension, it is not known whether normalizing blood pressure (BP) is beneficial and whether it reduces the risk of PE and SGA. This study examined whether controlling BP in patients with mild to moderate cHTN during pregnancy has a beneficial or adverse effect on PE or SGA risk. The researchers performed a systematic review and meta-analysis of randomized controlled trials of patients with mild to moderate cHTN in pregnancy that reported the effects of different levels of BP control on PE or SGA risk, including trials that compared treatment versus no treatment or versus placebo, in which control of BP after randomization was documented. Studies including women with gestational hypertension and cHTN were excluded unless they reported data separately for cHTN. The outcome measures for this analysis were superimposed PE and SGA. The researchers reviewed these outcome measures in relation to the level of BP control, defined as the difference in mean arterial pressure (MAP) after enrollment between the treated group and the controls. Six trials including 495 participants provided data on BP after entry to the study. Four studies compared antihypertensive agents to no treatment, and 2 studies compared antihypertensive agents to placebo. All trials were conducted between 1976 and 1990 and were considered to have a high risk of bias. There was high heterogeneity between studies for MAP after randomization (I~2 = 87%) and for SGA (I~2 = 60%), but not for PE (I~2 = 0%). There were large differences between studies in the inclusion criteria, antihypertensive regimens, targets of therapy, and gestational age range at entry to the trials. In women receiving antihypertensive therapy, compared with those receiving placebo or no treatment, the MAP after entry to the trial was significantly lower (mean difference, -4.2 mm Hg; 95% confidence interval [CI], -6.6 to -1.8; P = 0.006). However, there was no significant reduction in the risk of PE (relative risk [RR], 1.03; 95% CI, 0.63-1.68; P = 0.90) or SGA (RR, 1.01; 95% CI, 0.35-2.93; P = 0.99). The results suggest that lowering the MAP with antihypertensive medication in women with mild to moderate cHTN has no significant effect on PE or SGA risk. This study also found that the effect of antihypertensive medication in terms of lowering BP was significant but very small and that, in most trials, the average BP in the placebo or no treatment group was less than 140/90 mm Hg. The researchers acknowledge that the meta-analysis included a small number of trials with large heterogeneity and that the age of the studies may limit the conclusion because medical practice regarding care of these patients could have changed in the years since publication of the original trials. They recommend that future studies examine the impact of CH normalization of BP before conception and whether this approach would improve placentation and/or cardiovascular function and thereby prevent PE and SGA.