A Cochrane review included 46 studies with a total of 4 723 women with mild to moderate hypertension (systolic blood pressure 140 to 169 mmHg and diastolic blood pressure 90 to 109 mmHg). Twenty-nine trials compared an antihypertensive drug with placebo/no antihypertensive drug (3 350 women). All antihypertensive drugs halved the risk of severe hypertension; number needed to treat (NNT) 10, 95% CI 8 to 13. However, there was little evidence of a difference in the risk of pre-eclampsia, the risk of the baby dying, preterm birth, or small-for-gestational-age babies (table ). There were no clear differences in any other outcomes.
| Outcome | Relative risk (RR) | Participants (studies) |
|---|---|---|
| *Total reported fetal or neonatal death (including miscarriage) | ||
| Severe hypertension | 0.49 (0.40 to 0.60) | 2 558 (20 studies) |
| Pre-eclampsia | 0.93 (0.80 to 1.08) | 2 851 (23 studies) |
| Baby dying* | 0.71 (0.49 to 1.02) | 3 230 (27 studies) |
| Preterm birth | 0.96 (0.85 to 1.10) | 2 141 (15 studies) |
| Small-for-gestational-age babies | 0.97 (0.80 to 1.17) | 2 586 (20 studies) |
Twenty-two studies (n=1 723) compared one antihypertensive drug with another. When either beta blockers or calcium channel blockers were compared with methyldopa, they appeared to be more effective than methyldopa in avoiding an episode of severe hypertension (RR 0.54, 95% CI 0.30 to 0.95; 11 studies, n=638) and in reducing the overall risk of developing proteinuria/pre-eclampsia (RR 0.73, 95% CI 0.54 to 0.99; 11 studies, n=997). However, this effect was not seen in the subgroup analysis for beta blockers versus methyldopa or for calcium channel blockers versus methyldopa.