Hypertension, also referred to as high blood pressure, is the most common medical problem encountered during pregnancy, complicating 2 to 3 percent of pregnancies. It is important to treat hypertension during pregnancy since it can lead to serious pregnancy complications such as preeclampsia. However, not all antihypertensive agents are safe during pregnancy.
The drugs considered to be safe for treating mild and moderate hypertension during pregnancy are methyldopa, nifedipine and labetalol. More specifically, there are several studies that demonstrate the safety of methyldopa not only during pregnancy, but also during the 5 to 10 years following childbirth. The safety records of labetalol and nifedipine are not as well established as those of methyldopa.
Methyldopa is a central alpha-2 receptor agonist, which acts on total peripheral resistance (TPR) and cardiac output, and consequently lowers blood pressure. Labetalol lowers blood pressure by blocking several adrenergic receptors and reducing peripheral vascular resistance. The effects of labetalol on heart rate or cardiac output are minimal. Nifedipine is a calcium-channel blocker. As suggested by its name, nifedipine blocks calcium channels in muscle cells in the heart and blood vessels, and consequently, reduces muscle contraction and increases blood vessel diameter. As a result, both cardiac output and total peripheral resistance are bought down, leading to lower blood pressure.
In the United States, about 1 in 100 pregnancies is complicated by preexisting hypertension. About 1 in 20 pregnancies is complicated by gestational hypertension (high blood pressure developed during pregnancy). The rate of preeclampsia is 1 to 2 percent.
Hypertension is one of the major causes for pregnancy complications and maternal mortality. Pregnancy-induced hypertension is responsible for 16 to 20 percent of all maternal deaths in America. Hypertensive disorder also increases the risk of fetal growth restriction, eclamptic seizures, pulmonary edema, intracerebral hemorrhage, intrauterine fetal death and premature delivery. Thus, it is very important to keep blood pressure under control during pregnancy.
Since methyldopa can go into breast milk, consult with your doctor about the use of methyldopa during breast feeding. Avoid the following classes of antihypertensive agents during pregnancy: ACE inhibitors, diuretics and beta-blockers. These medications have been shown to have adverse effects on the fetus, including growth retardation, respiratory distress syndrome and prepartum death.