High blood pressure (hypertension) during pregnancy is classified as one of the following:
Preeclampsia is another type of high blood pressure that develops during pregnancy, but it is diagnosed and treated differently from other types of high blood pressure (see see Preeclampsia and Eclampsia).
Women who have chronic hypertension are more likely to have potentially serious problems during pregnancy. However, the following problems are more likely to occur if either chronic or gestational hypertension is present:
During pregnancy, women with high blood pressure are monitored closely to make sure blood pressure is well-controlled, the kidneys are functioning normally, and the fetus is growing normally. However, premature detachment of the placenta cannot be prevented or anticipated. Often, a baby must be delivered early to prevent stillbirth or complications due to severe high blood pressure (such as stroke) in the woman.
Treatment of mild high blood pressure (140/90 to 150/100 millimeters of mercury [mm Hg]) depends on many factors. Doctors may recommend reducing physical activity to possibly help lower blood pressure. If reduced activity does not lower blood pressure, many experts recommend treatment with antihypertensive drugs. Whether the benefits of these drugs outweigh the risks is unclear. However, if the kidneys are not functioning normally, drugs are needed. If high blood pressure is not controlled well, the kidneys may be damaged further.
If blood pressure is moderately high (150/100 to 180/110 mm Hg), treatment with antihypertensive drugs is recommended (see Table: Antihypertensive Drugs). Treatment can reduce the risk of stroke and other complications due to very high blood pressure.
If blood pressure is very high (180/110 mm Hg or higher), women are evaluated immediately because risk of complications for women and/or the fetus is high. If women wish to continue the pregnancy despite the risk, they often require several antihypertensive drugs. They may be hospitalized toward the end of the pregnancy. If their condition worsens, doctors may recommend ending the pregnancy.
Women are taught to check their blood pressure at home. Doctors periodically do tests to determine how well the kidneys are functioning and ultrasonography to determine how well the fetus is growing.
If pregnant women have moderately high or very high blood pressure, the baby is typically delivered at 38 to 39 weeks. It is delivered earlier if the fetus is growing slowly, the fetus is having problems, or the woman has severe preeclampsia.
Most antihypertensive drugs used to treat high blood pressure can be used safely during pregnancy. They include methyldopa, beta-blockers (such as labetalol), and calcium channel blockers. However, angiotensin-converting enzyme (ACE) inhibitors are stopped during pregnancy, particularly during the last two trimesters. These drugs can cause birth defects of the urinary tract in the fetus. As a result, the baby may die shortly after birth. Aldosterone antagonists (spironolactone and eplerenone) are also stopped because they can cause a male fetus to develop feminine characteristics. Thiazide diuretics (such as hydrochlorothiazide) are usually stopped during pregnancy. These diuretics increase the risk that the fetus will not grow as much as expected.
Last full review/revision September 2013 by Lara A. Friel, MD, PhD