Chronic hypertension is high blood pressure that is diagnosed before pregnancy, or before the 20th week of pregnancy. This type of high blood pressure does not go away after delivery. Medical experts do not fully understand what causes chronic hypertension. Genes, diet and lifestyle may play a role.

Hypertension may narrow or tighten the blood vessels in the uterus that supply the baby with oxygen and nutrients. Hypertension during pregnancy can create severe risks for both mother and baby, including:

  • Health problems for the mother, such as heart attack and stroke.
  • Slow fetal growth and low birthweight.
  • Increased risk of preterm delivery.
  • Placental abruption (separation of the placenta from the uterine wall during delivery; this can cause heaving bleeding and shock, placing both mother and baby in danger).

The good news is that with proper prenatal care, serious problems associated with chronic hypertension can usually be prevented. In fact, most women with high blood pressure have healthy pregnancies. However, about 1 in 4 develops a dangerous condition called preeclampsia.

Why is high blood pressure during pregnancy a problem?

High blood pressure during pregnancy can cause problems for you and your baby:

  1. Chronic hypertension: High blood pressure can make your baby grow too slowly. This can hurt your baby’s health. Women with chronic hypertension are also more likely to get preeclampsia, which can be very dangerous.
  2. Preeclampsia: High blood pressure is not the main problem, but it is one of the main signs of this health condition. Preeclampsia can cause problems with your brain (headache and seizures), your eyes (blurred vision), your liver (pain in your belly), and your blood and other organs. It can make your baby grow slowly. If you get preeclampsia and seizures, you and your baby are at risk of dying.
  3. Transient hypertension: This condition does not cause any problems for you or your baby.

Normally, a woman’s blood pressure drops during her second trimester. Then it returns to normal by the end of the pregnancy. But in some women, blood pressure goes up very high in the second or third trimester. This is sometimes called pregnancy-induced hypertension. It needs treatment, but it usually goes away after the baby is born.

High blood pressure that started before pregnancy usually doesn’t go away after the baby is born.

A small rise in blood pressure may not be a problem. But your doctor will watch your pressure to make sure it does not get too high. The doctor also will check you for preeclampsia.

Very high blood pressure keeps your baby from getting enough blood and oxygen. This could limit your baby’s growth or cause the placenta to pull away too soon from the uterus. High blood pressure also could lead to stillbirth.


Preeclampsia is a pregnancy-related problem. The symptoms of preeclampsia include new high blood pressure after 20 weeks of pregnancy along with other problems, such as protein in your urine. Preeclampsia usually goes away after you give birth. In rare cases, blood pressure can stay high for up to 6 weeks after the birth.

Preeclampsia can be deadly for the mother and baby. It can keep the baby from getting enough blood and oxygen. It also can harm the mother’s liver, kidneys, and brain. Women with very bad preeclampsia can have dangerous seizures. This is called eclampsia.

What causes preeclampsia and high blood pressure during pregnancy?

Experts don’t know the exact cause of preeclampsia and high blood pressure during pregnancy. But they have some ideas about preeclampsia:

  • Preeclampsia seems to start because the placenta doesn’t grow the usual network of blood vessels deep in the wall of the uterus. This leads to poor blood flow in the placenta.
  • Preeclampsia may run in families. If your mother had preeclampsia while she was pregnant with you, you have a higher chance of getting it during pregnancy. You also have a higher chance of getting it if the mother of your baby’s father had preeclampsia.
  • The mother’s immune system may react to the father’s sperm, the placenta, or the baby.
  • Already having high blood pressure when you get pregnant raises your chance of getting preeclampsia.
  • Problems that can lead to high blood pressure, such as obesity, polycystic ovary syndrome, and diabetes, could raise your risk of preeclampsia.


High blood pressure usually doesn’t cause symptoms. But very high blood pressure sometimes causes headaches and shortness of breath or changes in vision.

Mild preeclampsia usually doesn’t cause symptoms, either. But preeclampsia can cause rapid weight gain and sudden swelling of the hands and face. Severe preeclampsia causes symptoms of organ trouble, such as a very bad headache and trouble seeing and breathing. It also can cause belly pain and decreased urination.

What you can do before pregnancy?

If you have hypertension, see your health care provider before trying to get pregnant. He or she can help you get your blood pressure under control before you’re pregnant. Your provider can also check to be sure that the drugs you’re taking are safe to use during pregnancy. He or she can tell you whether you need to change any of the drugs before becoming pregnant.

Here are some other things you can do before becoming pregnant:

  • Work with your provider to lower your blood pressure.
  • If losing weight will help control your blood pressure, use diet and exercise to help meet your weight-loss goals.
  • Take your blood pressure medicine as prescribed.
  • Quit smoking. Smoking damages blood vessel walls. It is especially dangerous for people with high blood pressure. Smoking also harms your baby.

What you can do during pregnancy?

To protect your health and the health of your baby during your pregnancy:

  • If you have high blood pressure, tell your health care provider early in your pregnancy.
  • Go to all your prenatal care visits.
  • If your provider tells you to, check your blood pressure and weight at home.

Sources: Family Doctor, March of Dimes

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