Chronic hypertension: effect of blood pressure control on pregnancy outcome.

OBJECTIVE: To examine whether in patients with CH and mild to moderate hypertension the level of control of blood pressure during pregnancy has a beneficial or adverse effect on the risk of PE or SGA.

METHODS: We performed a systematic review and meta-analysis of randomized controlled trials of patients with mild to moderate CH in pregnancy that reported the impact of different levels of control of blood pressure on the risk of PE or SGA. We completed a literature search through PubMed, Embase, Cinahl, Web of science, Cochrane CENTRAL Library Relative risks with random effect were calculated with their 95% confidence intervals (95%CI).

RESULTS: Six trials including 495 participants provided data on blood pressure (BP) after entry to the study. Four studies compared antihypertensive agents to no treatment and two studies compared antihypertensive agents to placebo. All trials were conducted between 1976 and 1990 and were considered to be at high risk of bias. There was high heterogeneity between studies for mean arterial pressure (MAP) after randomization (I2  = 87%) and SGA (I2  = 60%), but not for PE (I2  = 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 to those receiving placebo or no treatment, the MAP after entry to the trial was significantly lower (mean difference -4.2 mmHg, 95%CI -6.6 to -1.8; p = .006). However, there was no significant reduction in the risk of PE (relative risks (RR) 1.03, 95%CI 0.63-1.68; p = .90) or SGA (RR 1.01, 95%CI 0.35-2.93; p = .99).

CONCLUSIONS: The findings of the meta-analysis suggest that lowering the blood pressure by antihypertensive medication in women with mild to moderate hypertension in the context of CH has no significant effect on the risk of SGA or PE.