Blood Pressure Medicines During Pregnancy

Doctors have prescribed methyldopa for years to treat high blood pressure in pregnancy. Recently, however, as other medications have been judged more effective, it has been used less often. Studies have found no decrease in placental blood flow and no problems in children as old as 7.5 years who were exposed to the drug in the womb.

Labetalol has both alpha and beta blocking properties. The drug dilates blood vessels more than drugs that are only beta-blockers. Widely used, it has not been associated with any bad effects on the pregnancy.

Beta-blockers such as atenolol and metoprolol appear to be safe for use during pregnancy. Although some studies have associated the use of beta blockers with fetal growth problems, it remains unclear if the growth problems are a result of the medication or a result of the high blood pressure itself. For many women, the balance of risks and benefits favors using beta blockers.

Calcium channel blockers are used in pregnancy, and research indicates they are usually safe, especially when used later in the pregnancy. Mixing them with magnesium sulfate (a drug commonly used to treat preterm labor) can lead to a rapid and excessive blood-pressure decrease.

Diuretics can be considered, with close prenatal care, if the woman had been taking it regularly prior to pregnancy. Because diuretics work by decreasing the amount of fluid in the body’s blood vessels and because fluid volume is already a problem when women have preeclampsia, diuretics should be used very cautiously if the pregnancy is thought to be complicated by preeclampsia.

Hydralazine and labetalol are the two medicines used most commonly to treat severe high blood pressure that must be lowered immediately. Each can be given intravenously.

These medicines can cause poor fetal growth, a reduced amount of amniotic fluid, kidney failure in the baby and neonatal death. Many of these problems develop when ACE inhibitors are used late in pregnancy. ACE inhibitors are usually stopped as soon as pregnancy is diagnosed.

Though no adverse effects have been proven, it is suspected that these medications would cause the same problems as ACE inhibitors.