Antihypertensive drug therapy for mild to moderate hypertension during pregnancy

Mild-moderate hypertension during pregnancy is common. Antihypertensive drugs are often used in the belief that lowering blood pressure will prevent progression to more severe disease, and thereby improve outcome.

To assess the effects of antihypertensive drug treatments for women with mild to moderate hypertension during pregnancy.

Relevant trials were identified in the register of trials maintained by the Cochrane Pregnancy and Childbirth Group. In addition, the Cochrane Controlled Trial Register, MEDLINE, and EMBASE were searched. Date of last search: October 2000.

All randomised trials evaluating any antihypertensive drug treatment for mild to moderate hypertension during pregnancy, defined whenever possible as systolic blood pressure 140-169 mmHg and diastolic blood pressure 90-109 mmHg. Comparisons were of one or more antihypertensive drug(s) with placebo, with no antihypertensive drug, or with another antihypertensive drug, and where treatment was planned to continue for at least seven days.

Data were extracted independently by two reviewers.

Overall, this review includes 40 studies (3797 women), 24 of which compared an antihypertensive drug with placebo/no antihypertensive drug (2815 women). There is a halving in the risk of developing severe hypertension associated with the use of antihypertensive drug(s) [17 trials, 2155 women; relative risk (RR) 0.52 (95% confidence interval (CI) 0.41 to 0.64); risk difference (RD) -0.09 (-0.12 to -0.06); number needed to treat (NNT) 12 (9 to 17)] but little evidence of a difference in the risk of pre-eclampsia [19 trials, 2402 women; RR 0.99 (0.84 to 1.18)]. Similarly, there is no clear effect on the risk of the baby dying [23 trials, 2727 women; RR 0.71(0.46 to 1.09)], preterm birth [12 trials, 1738 women; RR 0.98 (0.85 to 1.13)], or small for gestational age babies [17 trials, 2159 women; RR 1.13 (0.91 to 1.42)]. There were no clear differences in any other outcomes. Seventeen trials (1182 women) compared one antihypertensive drug with another. There is no clear difference between any of these drugs in the risk of developing severe hypertension, and proteinuria/pre-eclampsia. Other antihypertensive agents seem better than methyldopa for reducing the risk of the baby dying [14 trials, 1010 subjects, RR 0.49 (0.24 to 0.99); RD -0.02 (-0.04 to 0.00); NNT 45 (22 to 1341)]. Other outcomes were only reported by a small proportion of studies, and there were no clear differences.

It remains unclear whether antihypertensive drug therapy for mild-moderate hypertension during pregnancy is worthwhile.