What’s the Concern About High Blood Pressure During Pregnancy? An Ob-Gyn Explains.

Blood pressure is one of the vital signs we pay close attention to throughout pregnancy. When that cuff squeezes your upper arm, it measures how hard blood is pumping throughout your body. You may not remember your blood pressure reading from one prenatal visit to the next. But those numbers mean a lot to your ob-gyn.

Here’s what I want you to know about high blood pressure, or hypertension, during pregnancy.

An Inside Look

Your body goes through many changes during pregnancy, both inside and outside. The cardiovascular system is no exception. Your heart works a little harder and your blood vessels relax more than usual while you are pregnant. These changes help support your growing body while supplying blood and nutrients to the fetus.

Your blood pressure is measured as two numbers. The top number is the pressure against the artery walls when the heart contracts (systolic), and the bottom number is the pressure against the artery walls when the heart relaxes (diastolic). Anything under 120/80 is considered normal.

In a typical pregnancy, blood pressure tends to decrease slowly, reaching its lowest point at about 28 weeks. Your numbers usually trend toward a normal (non-pregnant) range before you give birth.

High blood pressure is common in this country, so some people will already have it when they get pregnant. Others will develop new blood pressure problems in the second half of pregnancy.

If you develop high blood pressure during pregnancy, and other organs aren’t yet affected, this is called gestational hypertension. We diagnose gestational hypertension when your top number is greater than 140, or your bottom number is greater than 90, or both. If other organs are also affected, this is called preeclampsia.

Complications of Gestational Hypertension

High blood pressure puts extra stress on your body and is always cause for concern. If left untreated, it can cause kidney failure, stroke, heart attack, even heart failure. The higher the blood pressure numbers, the greater the risk.

Pregnant women with high blood pressure are at risk of preterm birth and having babies who are smaller than normal. They are also more likely to have a cesarean birth.

Another possible complication is placental abruption, a serious condition that occurs when the placenta starts to separate from the wall of the uterus. This can be a medical emergency.

When Hypertension Becomes Preeclampsia

When high blood pressure starts to affect other organs, like your kidneys or liver, it is called preeclampsia. Another sign of preeclampsia is too much protein in the urine. Preeclampsia can happen during pregnancy or in the weeks after you give birth. It is a very serious condition.

If your condition worsens, you may develop what we call “severe features” of preeclampsia, such as blood pressure that exceeds 160 (systolic) or 110 (diastolic), severe headaches that don’t go away, and fluid in the lungs. Preeclampsia can lead to seizures, a condition called eclampsia.

Who Is at Risk

Any health condition that damages your blood vessels can increase your risk for blood pressure problems. Some of the most common conditions that may affect blood pressure are obesity, diabetes mellitus, kidney disease, and autoimmune conditions such as lupus. We also tend to see high blood pressure in pregnant women who are either in their teens or over 35.

If you had preeclampsia in a previous pregnancy, you are at risk for having high blood pressure in future pregnancies. The risk of preeclampsia coming back increases with each pregnancy.

A daily dose of baby aspirin may reduce the risk of preeclampsia in some women. Talk with your ob-gyn about whether you should take aspirin.

What to Look for

Keep in mind, blood pressure problems can happen to anyone. Warning signs of preeclampsia include nausea, a headache that doesn’t go away, swelling in your face and hands, and changes in your vision. Also be aware of pain in your upper-right abdomen, where your liver is. Tell your ob-gyn right away if you have any of these signs.

Again, your ob-gyn will check your blood pressure at every prenatal visit. They will also track the growth of your fetus with ultrasound. And early evidence of preeclampsia may come from your urine samples and blood work.

Long-Term Effects

Even if blood pressure problems get better after birth, the effects can last a lifetime. Women with gestational hypertension or preeclampsia are at higher risk of heart disease and kidney disease in the future.

All of your doctors—not just your ob-gyn—should know if you had high blood pressure or preeclampsia during or after pregnancy. This is important information to share with your health care team, whether they ask about it or not.

Options for Treatment

No matter how or when you develop high blood pressure, the health of your pregnancy greatly depends on how well it is managed. Your ob-gyn will work with you to treat high blood pressure and hopefully prevent preeclampsia.

Oral medications may be necessary to control existing hypertension or to manage gestational hypertension until you give birth. You may need to check your blood pressure at home between visits, too.

With severe preeclampsia, we can prevent seizures with a medication called magnesium sulfate, which needs to be given in a hospital. In some cases, the safest choice is to deliver right away.

Tiffany’s Story

I once knew an 18-year-old patient, “Tiffany,” who was enjoying a healthy, uneventful pregnancy. At 26 weeks, she started having heartburn and pain in her upper abdomen. Her mother-in-law, a nurse, checked her blood pressure. It was 180/115, and they immediately went to the hospital. Tiffany had a rare type of preeclampsia called HELLP syndrome. She was so sick the only treatment was to deliver the baby right away.

While Tiffany recovered after a few days in the hospital, her very premature baby had a long road ahead of her. But the outcome could have been even worse if her mother-in-law hadn’t thought to check her blood pressure.

Trust Your Gut

I’ve treated too many patients who felt something was wrong but waited too long to call. This is one of the greatest dangers with preeclampsia.

So if something doesn’t feel right, don’t explain it away. Let your ob-gyn know. Most of the time, it turns out to be regular pregnancy stuff—and that’s OK. We’d rather you call. That gives us the best ability to help.

Copyright 2024 by the American College of Obstetricians and Gynecologists. All rights reserved. Read copyright and permissions information.

This information is designed as an educational aid for the public. It offers current information and opinions related to women's health. It is not intended as a statement of the standard of care. It does not explain all of the proper treatments or methods of care. It is not a substitute for the advice of a physician. Read ACOG’s complete disclaimer.