Antihypertensive drug therapy for mild to moderate hypertension during pregnancy

There is not enough evidence to show whether antihypertensive drug treatment for mild to moderate hypertension during pregnancy is worthwhile.

During the early weeks of normal pregnancy, blood pressure falls and climbs slowly in later pregnancy to reach pre-pregnancy levels at term. Mild to moderate hypertension (high blood pressure) is common during pregnancy. In some women, it can become more serious, resulting in hospital admission, pre-eclampsia (a complication of pregnancy that includes high blood pressure) and possible premature delivery. Antihypertensive drugs are often used to lower blood pressure in the belief that they will prevent this progression. This review of 49 trials, involving 4723 women, found there was not enough evidence to show the benefit of antihypertensive drugs for mild to moderate hypertension during pregnancy. More research is needed.

Authors' conclusions: 

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

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Background: 

Mild to 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 the outcome.

Objectives: 

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

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 April 2013) and reference lists of retrieved studies.

Selection criteria: 

All randomised trials evaluating any antihypertensive drug treatment for mild to moderate hypertension during pregnancy defined, whenever possible, as systolic blood pressure 140 to 169 mmHg and diastolic blood pressure 90 to 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 collection and analysis: 

Two review authors independently extracted data.

Main results: 

Forty-nine trials (4723 women) were included. Twenty-nine trials compared an antihypertensive drug with placebo/no antihypertensive drug (3350 women). There is a halving in the risk of developing severe hypertension associated with the use of antihypertensive drug(s) (20 trials, 2558 women; risk ratio (RR) 0.49; 95% confidence interval (CI) 0.40 to 0.60; risk difference (RD) -0.10 (-0.13 to -0.07); number needed to treat to harm (NNTH) 10 (8 to 13)) but little evidence of a difference in the risk of pre-eclampsia (23 trials, 2851 women; RR 0.93; 95% CI 0.80 to 1.08). Similarly, there is no clear effect on the risk of the baby dying (27 trials, 3230 women; RR 0.71; 95% CI 0.49 to 1.02), preterm birth (15 trials, 2141 women; RR 0.96; 95% CI 0.85 to 1.10), or small-for-gestational-age babies (20 trials, 2586 women; RR 0.97; 95% CI 0.80 to 1.17). There were no clear differences in any other outcomes.

Twenty-two trials (1723 women) compared one antihypertensive drug with another. Alternative drugs seem better than methyldopa for reducing the risk of severe hypertension (11 trials, 638 women; RR (random-effects) 0.54; 95% CI 0.30 to 0.95; RD -0.11 (-0.20 to -0.02); NNTH 7 (5 to 69)). There is also a reduction in the overall risk of developing proteinuria/pre-eclampsia when beta blockers and calcium channel blockers considered together are compared with methyldopa (11 trials, 997 women; RR 0.73; 95% CI 0.54 to 0.99). However, the effect on both severe hypertension and proteinuria is not seen in the individual drugs. Other outcomes were only reported by a small proportion of studies, and there were no clear differences.