Pregnancy Induced Hypertension | Pregnancy and High Blood Pressure

Blood pressure is the force of the blood pushing against the walls of the arteries (blood vessels that carry oxygen-rich blood to all parts of the body). When the pressure in the arteries becomes too high, it is called hypertension.

Up to 5 percent of women have hypertension before they become pregnant.¹ This is called chronic hypertension. Another 5 to 8 percent develop hypertension during pregnancy.² This is referred to as gestational hypertension. Gestational hypertension generally goes away soon after delivery; however, women who develop it may be at increased risk of developing hypertension later in life.

High blood pressure usually causes no noticeable symptoms, whether or not a woman is pregnant. However, hypertension during pregnancy can cause serious complications for mother and baby. Fortunately, serious problems usually can be prevented with proper prenatal care.

How is blood pressure measured?
A pregnant woman’s blood pressure is measured at each prenatal visit. The health care provider measures blood pressure with an inflatable cuff that wraps around the upper arm. The pressure in the arteries is measured as the heart contracts (systolic pressure) and when the heart is relaxed between contractions (diastolic pressure). The blood pressure reading is given as two numbers, with the top number representing the systolic and bottom number the diastolic pressure—for example, 110/80. A systolic reading of 140 or higher, or a diastolic reading of 90 or higher is considered high blood pressure. Because blood pressure can go up and down during the day, health care providers often re-check a high reading with one or more additional readings to determine if a woman truly has high blood pressure.

What is chronic hypertension?
Chronic hypertension is defined as high blood pressure that is diagnosed before pregnancy or before the 20th week of pregnancy. This form of hypertension does not go away after delivery.

The causes of chronic hypertension are not thoroughly understood, although heredity, diet and lifestyle are believed to play a role. Untreated hypertension can increase the risk of serious health problems such as heart attack and stroke.

Women with chronic hypertension should see their health care provider before attempting to conceive. A pre-pregnancy visit allows the provider to ensure that the blood pressure is under control, and to evaluate any medication the woman takes to control her blood pressure. While some medications to lower blood pressure are safe during pregnancy, others—including a group of drugs called angiotensin-converting-enzyme (ACE) inhibitors—can harm the fetus. Some women with chronic hypertension may be able to stop taking their medication or reduce their dose, at least during the first half of pregnancy, as blood pressure tends to fall during this time. However, blood pressure needs to be monitored carefully during this period.

Most women with chronic hypertension have healthy pregnancies. However, about 25 percent develop a form of gestational hypertension called preeclampsia (see below), which poses special risks.^2,3