Hydralazine is associated with poorer maternal and perinatal outcomes than labetalol and nifedipine, is less effective than nifedipine or isradipine, and doesn't differ significantly in performance from labetalol, according to a meta-analysis of randomized, controlled clinical trials.
Researchers from British Columbia reviewed 21 randomized, controlled trials published between 1966 and 2002 and involving 1085 women taking short-acting antihypertensives for severe hypertension in pregnancy. They found that hydralazine was associated with more maternal hypotension, caesarean section delivery, placental abruption, maternal oliguria, adverse effects on fetal heart rate, and low Apgar scores at 1 minute than the alternatives. It was also more poorly tolerated, with a greater incidence of headaches, palpitations, and maternal tachycardia than was associated with other antihypertensives, with the possible exception of nifedipine.
While the heterogeneity of their findings made them insufficiently robust to recommend broad alterations in clinical practice, the authors did suggest nifedipine and parenteral labetalol as reasonable alternatives to hydralazine.
Magee LA, Cham C, Waterman EJ, et al. Hydralazine for treatment of severe hypertension in pregnancy: meta-analysis. BMJ. 2003;327:955-960.