High blood pressure, or hypertension, is defined as blood pressure greater than or equal to 130/80 mm Hg. The condition is a serious concern for some pregnant women. When it’s well-managed, high blood pressure during pregnancy isn’t always dangerous. But it can sometimes cause severe health complications for both mother and developing baby.

What causes high blood pressure during pregnancy?

There are several possible causes of high blood pressure during pregnancy.

These include:

• being overweight or obese
• not getting enough physical activity
• smoking
• drinking alcohol
• first-time pregnancy
• a family history of pregnancy-related hypertension
• carrying more than one child
• age (over 35)
• assistive reproductive technology (such as in vitro fertilization, or IVF)
• having diabetes or certain autoimmune diseases

Risk factors for high blood pressure during pregnancy

There are a few risk factors that could make high blood pressure more likely during pregnancy.

• Lifestyle

Unhealthy lifestyle choices may lead to high blood pressure during pregnancy. Being overweight or obese, or not staying active are major risk factors for high blood pressure.

• Type of pregnancy

Women experiencing their first pregnancy are more likely to have high blood pressure. Fortunately, there’s a lower chance of this condition in subsequent pregnancies. Carrying multiples can make it more likely for a woman to develop hypertension, because the body is working harder to nourish more than one baby.

• Age

Age can also be a factor. Pregnant women over the age of 35 are at higher risk. Women who had high blood pressure before pregnancy are at higher risk for related complications during pregnancy than those with normal blood pressure.

Types of pregnancy-related blood pressure conditions

High blood pressure during pregnancy can be divided into three different conditions.

• Chronic hypertension

Sometimes a woman has preexisting high blood pressure, or hypertension, before she gets pregnant. This may be referred to as chronic hypertension and is usually treated with blood pressure medication. Doctors also consider hypertension that occurs in the first 20 weeks of pregnancy to be chronic hypertension.

• Gestational hypertension

Gestational hypertension develops after the 20th week of pregnancy. It usually resolves after delivery. When diagnosed before 30 weeks, there’s a higher chance it will progress to preeclampsia.

• Chronic hypertension with superimposed preeclampsia

Women who have chronic hypertension before becoming pregnant can develop preeclampsia. This occurs when they experience protein in their urine or additional complications as the pregnancy progresses.

Tracking blood pressure during pregnancy

A blood pressure reading is a fraction: your systolic blood pressure over your diastolic blood pressure. The top number is your systolic pressure, which is a measurement of the pressure on your arteries when the heart is beating or squeezing blood forward through your body. The diastolic pressure, or the lower number, is a measurement of the blood pressure in your arteries when the heart is at rest.

What is considered normal blood pressure during pregnancy?

To determine what your “normal” blood pressure is during pregnancy, your doctor will likely take a baseline blood pressure measurement at your first visit. Then they will measure your blood pressure at every visit that follows.

Normal blood pressure is anything less than 120/80 mm Hg.

What is considered high blood pressure during pregnancy?

A blood pressure that is greater than 130/90 mm Hg or that is 15 degrees higher on the top number from where you started before pregnancy may be cause for concern.

High blood pressure during pregnancy is defined as 140 mm Hg or higher systolic, with diastolic 90 mm Hg or higher.

Early in pregnancy, usually from 5 weeks to the middle of the second trimester, a pregnant woman’s blood pressure may actually decrease. This is because pregnancy hormones can stimulate blood vessels to widen. As a result, the resistance to blood flow isn’t as high.

What is considered low blood pressure during pregnancy?

While there isn’t a definitive number that is too low, there are symptoms that are associated with low blood pressure:

• headache
• dizziness
• nausea
• feeling faint
• cold, clammy skin

Changes in blood pressure during pregnancy

As a woman progresses in her pregnancy, her blood pressure may change or return to pre-pregnancy levels. There are a few possible reasons for this. The amount of blood in a woman’s body increases. This is extra blood that the heart must pump throughout the body. The left ventricle (left side of the heart that does a significant amount of pumping) becomes thicker and larger. This temporary effect allows the heart to work harder to support the increased blood volume. The kidneys release increased amounts of vasopressin, a hormone that leads to increased water retention. In most cases, high blood pressure during pregnancy will decrease after the baby is delivered. In cases where blood pressure remains elevated, your doctor may prescribe medication to get it back to normal.

Tips for tracking blood pressure during pregnancy

There are ways to track your blood pressure between doctor visits.

You can buy a blood pressure monitor from a pharmacy or online medical goods store. Many of these devices will go on your wrist or upper arm. To check the monitor’s accuracy, take it to your doctor’s office and compare the readings on the monitor to those from your doctor. Visit a grocery store, pharmacy, or other store that has a machine that takes blood pressure readings. For the most accurate readings, take your blood pressure at the same time every day. Take it while seated with your legs uncrossed. Use the same arm each time.

Notify your doctor immediately if you have repeated high blood pressure readings that are four hours apart or symptoms of high blood pressure.

What are the complications of high blood pressure during pregnancy?

If you have high blood pressure during pregnancy, there can be complications.

Preeclampsia

This condition can cause serious damage to your organs, including your brain and kidneys. Preeclampsia is also known as toxemia. Preeclampsia with seizures becomes eclampsia. If left untreated, it can be fatal.

Symptoms of preeclampsia include:

• abnormal swelling in hands and face
• persistent headaches
• seeing spots or having changes in vision
• upper abdominal pain
• nausea or vomiting later in pregnancy
• difficulty breathing

Because preeclampsia can be dangerous for both you and your baby, you should call your doctor if you have any of these symptoms. Keeping regular doctor visits and letting your doctor know about any changes can help them catch and treat preeclampsia early.

HELLP syndrome

HELLP is an acronym that stands for hemolysis, elevated liver enzymes, and low platelet count. This condition is severe and life-threatening and can be a complication of preeclampsia.

Symptoms associated with HELLP include:

• nausea
• vomiting
• headache
• upper abdominal pain

Because HELLP syndrome can severely damage organ systems vital to life, emergency medical care is aimed at reducing blood pressure for the health of the mother and the baby. In some cases, a premature delivery is required.

High blood pressure during pregnancy can also have an effect on the baby’s growth rate. This can result in low birth weight.

Preventing high blood pressure during pregnancy

Common risk factors for high blood pressure, such as obesity, can be minimized through diet and exercise. During pregnancy, it’s normal to gain some weight. If you’re concerned, talk to your doctor about a target weight gain and ways to stay within a range that’s healthy for you.

Dietary guidelines for pregnant women vary from person to person. A nutritionist can help create a meal plan that’s designed for your specific height and weight. Avoid smoking and drinking alcohol. Both are known to raise blood pressure and to cause other complications during pregnancy. Salt is important during pregnancy and it’s usually not necessary. Limit salt intake, even for women with high blood pressure. Restricting salt too much is harmful for pregnant women and can impact fetal growth and development.

Pregnancy causes hormone shifts as well as psychological and physical changes. This can bring on stress, which can make high blood pressure harder to manage. Try stress reduction techniques such as yoga and meditation.