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

Blood pressure that is 140/90 millimeters of mercury (mm Hg) or greater — documented on two occasions, at least four hours apart — is abnormal and considered too high (hypertension).

Having hypertension during pregnancy requires close monitoring. Here's what you need to know.

What are the types of high blood pressure during pregnancy?

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

  • 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 hypertension before pregnancy who develop worsening high blood pressure and protein in the urine or other blood pressure related complications during pregnancy.
  • Preeclampsia. Preeclampsia occurs when hypertension develops after 20 weeks of pregnancy, and 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, including development of seizures (eclampsia).

    Previously, preeclampsia was diagnosed only if a pregnant woman had high blood pressure and protein in her urine. Experts now know that it's possible to have preeclampsia without having 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 (intrauterine growth restriction), low birth weight or premature birth. Prematurity can lead to breathing problems, increased risk of infection and other complications for the baby.
  • Placental abruption. Preeclampsia increases your risk of this condition in which the placenta separates from the inner wall of your uterus before delivery. Severe abruption can cause heavy bleeding, which can be life-threatening for you and your baby.
  • Intrauterine growth restriction. Hypertension might result in slowed or decreased growth of your baby (intrauterine growth restriction).
  • Injury to your other organs. Poorly controlled hypertension can result in injury to your brain, 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 potentially life-threatening complications when you have high blood pressure during pregnancy.
  • Future cardiovascular disease. Having preeclampsia might increase your risk of future heart and blood vessel (cardiovascular) disease. Your risk of future cardiovascular disease is higher if you've had preeclampsia more than once or you've had a premature birth due to having high blood pressure during pregnancy.

How will I know if I develop hypertension during pregnancy?

Monitoring your blood pressure is an important part of prenatal care. Blood pressure that is 140/90 mm Hg or greater — documented on two occasions, at least four hours apart — is abnormal and requires additional care.

How will I know if I develop preeclampsia?

Besides high blood pressure, other signs and symptoms of preeclampsia 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 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 they also occur in many normal pregnancies, so weight gain and swelling aren't 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 II receptor blockers and renin inhibitors — are generally avoided during pregnancy.

Treatment is important, however. High blood pressure puts you at risk of heart attack, stroke and other major complications. And it 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 at the most appropriate dose. Take the medication exactly as prescribed. Don't stop taking the medication or adjust the dose on your own.

Aug. 15, 2017 See more In-depth