Having high blood pressure (hypertension) during pregnancy needs close monitoring. Here's what to know about the potential risks. Also learn how to take care of yourself and your baby.

Sometimes high blood pressure begins before pregnancy. In other cases, the condition develops during pregnancy.

• Chronic hypertension. In chronic hypertension, high blood pressure develops either before pregnancy or during the first 20 weeks of pregnancy. Because high blood pressure usually doesn't have symptoms, it might be hard to know exactly when it began.
• Chronic hypertension with superimposed preeclampsia. This condition occurs when chronic hypertension leads to worsening high blood pressure during pregnancy. People with this condition may develop protein in the urine or other complications.
• Gestational hypertension. People with gestational hypertension have high blood pressure that develops after 20 weeks of pregnancy. There's no excess protein in the urine and there are no other signs of organ damage. But in some cases, gestational hypertension can eventually lead to preeclampsia.
• Preeclampsia. Preeclampsia occurs when hypertension develops after 20 weeks of pregnancy. Preeclampsia is associated with signs of damage to other organ systems, including the kidneys, liver, blood or brain.

Untreated preeclampsia can lead to serious — even fatal — complications for mother and baby. Complications may include eclampsia, in which seizures develop.

Previously, preeclampsia was diagnosed only when both high blood pressure and protein in the urine were present. Experts now know that it's possible to have preeclampsia without having protein in the urine.

High blood pressure during pregnancy poses the following risks:

• Less blood flow to the placenta. If the placenta doesn't get enough blood, the fetus might receive less oxygen and fewer nutrients. This can lead to slow growth (intrauterine growth restriction), low birth weight or premature birth. Babies born early can have breathing problems, increased risk of infection and other complications.
• Placental abruption. In this condition, the placenta separates from the inner wall of the uterus before delivery. Preeclampsia and high blood pressure increase the risk of placental abruption. Severe abruption can cause heavy bleeding, which can be life-threatening for you and your baby.
• Intrauterine growth restriction. High blood pressure might result in slowed or decreased fetal growth.
• Injury to other organs. Poorly controlled high blood pressure can result in injury to the brain, eyes, heart, lungs, kidneys, liver and other major organs. In severe cases, it can be life-threatening.
• Premature delivery. Sometimes an early delivery is needed to prevent life-threatening complications from high blood pressure during pregnancy.
• Future cardiovascular disease. Having preeclampsia might increase the risk of future heart and blood vessel (cardiovascular) disease. The risk of future cardiovascular disease is higher if you've had preeclampsia more than once. It's also higher if you've had a premature birth due to having high blood pressure during pregnancy.

Monitoring your blood pressure is an important part of prenatal care. If you have chronic hypertension, your health care provider will consider these categories for blood pressure measurements:

• Elevated blood pressure. Elevated blood pressure is a systolic pressure ranging from 120 to 129 millimeters of mercury (mm Hg) and a diastolic pressure below 80 mm Hg. Elevated blood pressure tends to get worse over time unless steps are taken to control it.
• Stage 1 hypertension. Stage 1 hypertension is a systolic pressure ranging from 130 to 139 mm Hg or a diastolic pressure ranging from 80 to 89 mm Hg.
• Stage 2 hypertension. This stage is more severe. It's a systolic pressure of 140 mm Hg or higher or a diastolic pressure of 90 mm Hg or higher.

After 20 weeks of pregnancy, blood pressure that's higher than 140/90 mm Hg without any other organ damage is considered to be gestational hypertension. Blood pressure needs to be taken and documented on two or more occasions, at least four hours apart.

In addition to high blood pressure, other signs and symptoms of preeclampsia include:

• Extra protein in the urine or other signs of kidney problems
• Severe headaches
• Changes in vision, including temporary loss of vision, blurred vision or being sensitive to light
• Upper stomach pain, usually under the ribs on the right side
• Nausea or vomiting
• Decreased levels of platelets in the blood
• Impaired liver function
• Shortness of breath, caused by fluid in the lungs

Sudden weight gain and swelling — particularly in the face and hands — often occurs with preeclampsia. The swelling associated with preeclampsia is more severe than the typical swelling that happens during pregnancy.

Some blood pressure medications are considered safe to use during pregnancy. However, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers and renin inhibitors need to be avoided during pregnancy.

Treatment is important. High blood pressure increases your risk of heart attack, stroke and other major complications. And high blood pressure can be dangerous for your baby.

If you need medication to control your blood pressure during pregnancy, your health care provider will prescribe the safest medication and dose. Take the medication exactly as prescribed. Don't stop taking it or change the dose on your own.

Low-dose daily aspirin often is recommended to lower the risk of preeclampsia in those who are at high risk. Studies have found aspirin to be safe during pregnancy.

If you have high blood pressure, schedule a preconception appointment with a health care provider who has expertise in managing pregnancies complicated by hypertensive disorders. Also meet with other members of your health care team, such as your primary care provider or cardiologist. They'll look at how well you're managing your high blood pressure. They also may consider treatment changes before you get pregnant.

If you're overweight, your health care provider will recommend losing weight before becoming pregnant.

During pregnancy, you'll see your health care provider often. Your weight and blood pressure will be checked at every visit. You also might need frequent laboratory tests.

Your health care provider will closely monitor your baby's health, as well. Frequent ultrasounds might be used to track growth. Fetal testing might be used to evaluate your baby's well-being. Your health care provider might also recommend that you track your baby's daily movements.

Taking good care of yourself is the best way to take care of your baby. For example:

• Keep your prenatal appointments. Visit your health care provider on a regular basis throughout your pregnancy.
• Take your blood pressure medication and low-dose daily aspirin as prescribed. Your health care provider will prescribe the safest medication at the most appropriate dose.
• Stay active. Follow your health care provider's recommendations for physical activity.
• Eat a healthy diet. Ask to speak with a dietitian if you need help planning meals.
• Know what's off-limits. Avoid smoking, alcohol and illegal drugs. Talk to your health care provider before taking nonprescription medications.

Researchers continue to study ways to prevent preeclampsia. Studies suggest that low-dose aspirin lowers the risk of preeclampsia in those who are at high risk. The American College of Obstetricians and Gynecologists recommends that they take a daily low-dose aspirin (81 milligrams) starting late in the first trimester.

Your health care provider might recommend inducing labor before your due date to avoid complications. The timing is based on how well controlled your blood pressure is and whether you have end-stage organ damage. It also depends on whether your baby has complications, such as slow growth.

If you have preeclampsia and the condition is getting worse, you might be given medication during labor to help prevent seizures.

Breastfeeding is encouraged for most who have high blood pressure, even those who take medication. Discuss your medications with your health care provider before your baby is born.