High blood pressure and pregnancy: Know the facts

High blood pressure and pregnancy isn't necessarily a dangerous combination. Here's what you need to know to take care of yourself — and your baby.

By Mayo Clinic Staff

Having high blood pressure (hypertension) during pregnancy — whether you develop the condition before or after conception — requires special care. Here's what you need to know about high blood pressure and pregnancy.

Are there different types of high blood pressure during pregnancy?

Sometimes high blood pressure is present before pregnancy. In other cases, high blood pressure develops during pregnancy. For example:

  • Gestational hypertension. Women with gestational hypertension have high blood pressure that develops after 20 weeks of pregnancy. There is no excess protein in the urine or other signs of organ damage. Some women with gestational hypertension eventually develop preeclampsia.
  • Chronic hypertension. Chronic hypertension is high blood pressure that was present before pregnancy or that occurs before 20 weeks of pregnancy. But because high blood pressure usually doesn't have symptoms, it might be hard to determine when it began.
  • Chronic hypertension with superimposed preeclampsia. This condition occurs in women with chronic high blood pressure before pregnancy who then develop worsening high blood pressure and protein in the urine or other health complications during pregnancy.
  • Preeclampsia. Sometimes chronic hypertension or gestational hypertension leads to preeclampsia, a pregnancy complication characterized by high blood pressure and signs of damage to another organ system — usually after 20 weeks of pregnancy. Left untreated, preeclampsia can lead to serious — even fatal — complications for mother and baby. Previously, preeclampsia was only diagnosed if a pregnant woman had high blood pressure and protein in her urine. However, experts now know that it's possible to have preeclampsia, yet never have protein in the urine.

Why is high blood pressure a problem during pregnancy?

High blood pressure during pregnancy poses various risks, including:

  • Decreased blood flow to the placenta. If the placenta doesn't get enough blood, your baby might receive less oxygen and fewer nutrients. This can lead to slow growth, low birth weight or preterm birth. Prematurity can lead to breathing problems for the baby.
  • Placental abruption. Preeclampsia increases your risk of placental abruption, in which the placenta separates from the inner wall of your uterus before delivery. Severe abruption can cause heavy bleeding and damage to the placenta, which can be life-threatening for both you and your baby.
  • Premature delivery. Sometimes an early delivery is needed to prevent potentially life-threatening complications.
  • Future cardiovascular disease. Having preeclampsia increases your risk of future heart and blood vessel (cardiovascular) disease. The risk is even greater if you've had preeclampsia more than once or you've had a premature birth. To minimize this risk, after delivery try to maintain your ideal weight, eat a variety of fruits and vegetables, exercise regularly, and don't smoke.

What do I need to know about preeclampsia?

Preeclampsia sometimes develops without any symptoms. High blood pressure might develop slowly, but more commonly it has a sudden onset. Monitoring your blood pressure is an important part of prenatal care because the first sign of preeclampsia is commonly a rise in blood pressure. Blood pressure that is 140/90 millimeters of mercury (mm Hg) or greater — documented on two occasions, at least four hours apart — is abnormal.

Other signs and symptoms of preeclampsia might include:

  • Excess protein in your urine (proteinuria) or additional signs of kidney problems
  • Severe headaches
  • Changes in vision, including temporary loss of vision, blurred vision or light sensitivity
  • Upper abdominal pain, usually under your ribs on the right side
  • Nausea or vomiting
  • Decreased urine output
  • Decreased levels of platelets in your blood (thrombocytopenia)
  • Impaired liver function
  • Shortness of breath, caused by fluid in your lungs

Sudden weight gain and swelling (edema) — particularly in your face and hands — often accompanies preeclampsia. But these things also occur in many normal pregnancies, so they're not considered reliable signs of preeclampsia.

Is it safe to take blood pressure medication during pregnancy?

Any medication you take during pregnancy can affect your baby. Although some medications used to lower blood pressure are considered safe during pregnancy, others — such as angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs) and renin inhibitors — are generally avoided during pregnancy.

Treatment is important, however. The risk of heart attack, stroke and other problems associated with high blood pressure doesn't go away during pregnancy. And high blood pressure can be dangerous for your baby, too.

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

Jul. 29, 2014 See more In-depth