Antihypertensive drugs in pregnancy

Abstract

When mean arterial pressure exceeds 140 mmHg (equivalent to 180/120), there is a significant risk of maternal cerebral vascular damage. Therefore it is recommended that blood pressures greater than 170/110 should be treated with urgency, aiming to maintain the blood pressure at all times at less than 170/110 but not lower than 130/90. Parenteral hydralazine is effective and safe therapy. Labetalol (intravenously or orally) appears to be as effective and as safe, and causes fewer troublesome side effects; however, clinical experience of its use is more limited, particularly in relation to its safety for the fetus and neonate. Delivery of the fetus is usually the definitive management of severe hypertension in pregnancy. However, this action may not reduce the blood pressure immediately. After initial treatment with rapid-acting agents, it is often advantageous to maintain control of arterial pressure with ongoing oral therapy (methyldopa, labetalol). In addition to the protective effect on the mother, such therapy may allow delivery of the fetus to be deferred; this should be considered only if the fetus is significantly premature (e.g., less than 34 weeks), there is no other evidence of maternal or fetal distress, and there can be meticulous monitoring of the maternal and fetal state proceeding to prompt delivery if deterioration occurs. The indications for treatment of mild or moderate hypertension in pregnancy are less clear. Severe hypertensive episodes can be reduced by several drugs (methyldopa, labetalol, beta-blockers). Methyldopa appears to reduce the small risk of mid-trimester abortions seen in association with early hypertension. Other benefits may be possible with other individual drugs; however, none of these have been found consistently in controlled studies to date. There seems, therefore, to be no definite indication for treatment of mild hypertension in pregnancy; treatment of moderate hypertension may be reasonable but its value is unproved at present. Antihypertensive drugs are valuable in pregnancy to reduce the risks directly due to elevated blood pressure. These drugs are not expected to affect the evolution of preeclampsia nor to treat the other complications of this condition.