Oral beta-blockers for mild to moderate hypertension during pregnancy.

backgroundHypertension is a common complication of pregnancy. Antihypertensive drugs are widely used in the belief these will improve outcome for both the woman (such as decreasing the risk of stroke or eclampsia) and her baby (such as decreasing the risk of preterm birth and its complications). Beta-blockers are a popular choice of antihypertensive agent during pregnancy; other choices include methyldopa and calcium channel blockers.

objectivesThe aim of this review is to assess whether oral beta-blockers are overall better than placebo, or no beta-blocker, for women with mild-moderate hypertension during pregnancy, and to assess whether oral beta-blockers have any advantages over other antihypertensive agents for women with mild-moderate hypertension during pregnancy. Both maternal outcomes (e.g., the incidence of severe hypertension) and perinatal outcomes (e.g., mortality) were of interest. SEARCH STRATEGY: Register of trials maintained by the Cochrane Pregnancy and Childbirth Group, MEDLINE 1966-97, bibliographies of retrieved papers, personal files. Date of last search: June 2000. SELECTION CRITERIA: Trials comparing beta-blockers with (i) placebo or no therapy, or (ii) other antihypertensive agents, for women with mild-moderate pregnancy hypertension (i.e., blood pressure under 170 mm Hg systolic, or 110 mm Hg diastolic). DATA COLLECTION AND ANALYSIS: All data were extracted independently by two investigators, who were not blinded to outcome or other trial characteristics. Whenever possible, missing data were obtained by personal communication with authors. Discrepancies were resolved by discussion. The overview was divided into two comparisons: (i) beta-blockers versus placebo or no therapy, and (ii) beta-blockers versus other antihypertensives. MAIN

resultsTwenty-seven trials, involving just under 2400 women, are included in this review. Fourteen trials (1516 women) compared beta-blockers with placebo/no beta blocker. Oral beta-blockers decrease the risk of severe hypertension (relative risk (RR) 0.37, 95% confidence interval (CI) 0.26-0.53) and the need for additional antihypertensive drugs (RR 0.44, 95% CI 0.31-0.62). There are insufficient data for any conclusions about the effect on perinatal mortality or preterm delivery. Beta-blockers seem to be associated with an increase in small for gestational age infants (RR 1.34, 95% CI 1.01-1.79). Maternal hospital admission may be decreased, neonatal bradycardia increased and respiratory distress syndrome decreased, but these outcomes are only reported in a very small proportion of trials. Eleven trials (787 women) compared beta-blockers with methyldopa. Beta-blockers appear to be no more effective and probably equally as safe (from maternal and perinatal perspectives) as methyldopa. Single small trials have compared beta-blockers with hydralazine and with nicardipine. It is unusual for women to change drugs due to side effects. REVIEWER'S

conclusionsThe improvement in control of maternal blood pressure with use of beta-blockers would be worthwhile only if it were reflected in other more substantive benefits for the mother and/or baby, and none have yet been clearly demonstrated. The effect of beta-blockers on perinatal outcome is uncertain, given that the worrying trend to an increase in small for gestational age infants is partly dependent on one small outlying trial. Large, randomised controlled trials are needed to determine whether antihypertensive therapy in general (rather than beta-blocker therapy specifically) results in benefits that outweigh the risks for treatment of mild-moderate pregnancy hypertension. If so, then it would be appropriate to look at which antihypertensive is best. Beta-blockers would remain a candidate class of agents.