High Blood Pressure In Pregnancy

by Michelle A. Finkel, MD

High blood pressure associated with pregnancy -- also called hypertension in pregnancy -- is defined as a blood pressure of greater than or equal to 140 mm Hg systolic (the top number in blood pressure readings) and greater than 90 mm Hg diastolic (the bottom number). It is not a disease itself, but is instead an umbrella term for a group of serious disorders that includes chronic high blood pressure (which starts before pregnancy), eclampsia, preeclampsia and a disorder called HELLP syndrome.

Hypertensive disorders of pregnancy were once called "toxemia" because scientists believed that an undiscovered toxin caused the dangerous conditions. While this theory is no longer in vogue, a clear cause of hypertensive disorders in pregnancy is still unknown. Even without a cause, however, it is still possible to ascribe general characteristics to the conditions. They are characterized by blood vessels that spasm and leak abnormally, and can vary from mild, isolated high blood pressure to very severe problems that require emergency care. Also, they almost always occur in the third trimester of pregnancy.

Blood Pressure in Normal Pregnancy

During a normal pregnancy your blood pressure drops, in part because all the blood vessels dilate (expand), lessening the force of the blood against the vessel walls. The top (systolic) number in the blood pressure reading will decrease slightly but the bottom number (diastolic) can fall considerably, beginning in the first trimester and continuing to the end of the second trimester. In the third trimester, blood pressure will return back to normal and should not be higher than 140/90. If high blood pressure is detected, your doctor should always repeat the reading to ensure its accuracy. Blood pressures that are on the borderline need to be followed very carefully to make certain they do not increase.

Chronic High Blood Pressure

Some women start pregnancy with an existing high blood pressure problem called chronic hypertension. If you are one of these women, you should talk to your doctor about your blood pressure before you get pregnant, or, at the latest, during your first prenatal visit. Patients with chronic high blood pressure may benefit from blood pressure-lowering medicines before and throughout their pregnancies. Therefore, if you have chronic hypertension you should expect to be on medication for this problem during your pregnancy.

Often, a class of medicines called beta blockers or a drug called methyldopa is used in this scenario. It is important that you take the blood pressure-lowering medicines your doctor prescribes because in pregnancy, chronic hypertension can develop into more severe high blood pressure problems with serious consequences. For example, chronic hypertension is a predisposing factor for preeclampsia, and treatment of chronic hypertension can reduce the risk of developing preeclampsia.

Preeclampsia

One of the reasons blood pressure is monitored so carefully during pregnancy is to prevent a condition called preeclampsia, a type of hypertensive disorder that occurs during pregnancy.

Preeclampsia is classically defined by three problems:

  • High blood pressure
  • Protein in the urine (a sign of kidney dysfunction)
  • Pathologic (abnormal) swelling

Protein in the urine cannot be seen by the naked eye; your doctor must find it by laboratory analysis. Pregnant women may experience bloating during their pregnancies, but swelling is considered abnormal when it is generalized, involving the hands, face or legs.

Preeclampsia occurs in 5% to 30% of all pregnancies, depending on the population and the precise definition of the disease. It is unique to humans, and occurs after the 20th week of pregnancy. Preeclampsia is potentially a very dangerous condition that can cause:

  • Kidney failure
  • Liver damage
  • Bleeding in the brain
  • Fluid on the lungs (called pulmonary edema)
  • Delay of the fetus' growth

Eclampsia

Eclampsia is another type of hypertension in pregnancy. It includes all the components of preeclampsia -- high blood pressure, abnormal swelling, and protein in the urine -- with the additional symptom of seizures. The seizures associated with eclampsia may be caused by tiny spots of bleeding in the head called petechial hemorrhages. These hemorrhages occur because the high blood pressure ruptures tiny blood vessels in the brain. Two percent of preeclamptic patients will progress to eclampsia.

An eclamptic patient is very ill, and needs medications for high blood pressure as well as for seizures. Patients with this disease are admitted to the hospital, usually to the intensive care unit. The mortality (death) rate of eclampsia is 8% to 36% for the patient and 13% to 30% for the fetus. The major cause of death for the patient is due to what are called intracranial hemorrhages -- large areas of bleeding in the head, not small, petechial, ones.

In both eclampsia and preeclampsia, there are a number of blood tests that the doctor will order to monitor the kidney, liver and other organs.

HELLP Syndrome

HELLP Syndrome is yet another type of hypertensive disorder that occurs in pregnancy. HELLP stands for:

Hemolysis (blood breakdown)
Elevated Liver enzymes (indicating liver problems)
Low Platelets (cells that help the blood clot normally)

HELLP patients are very sick and are managed right away in the hospital. The complications are similar to those of preeclampsia and eclampsia, including pulmonary edema, bleeding in the brain, liver and kidney disease, and fetal abnormalities and death.

Treatment

The goal of treatment for hypertensive disorders of pregnancy includes the prevention of maternal complications, the birth and development of a healthy baby, and the mother's future good health.

Ultimately, the high blood pressure of severe preeclampisa or eclampsia usually resolves upon delivery of the baby, and therefore delivery is considered definitive treatment for severe hypertension in late pregnancy.

Women with preexisting high blood pressure can be put on blood pressure-lowering medicines during pregnancy in an effort to prevent adverse consequences. As long as women with chronic hypertension are followed closely and demonstrate no complications they can maintain normal lifestyles. However, a woman whose blood pressures are consistently high or one who shows any of the signs described earlier -- kidney, liver, lung, or blood clotting problems -- needs to be managed more urgently in the hospital.

These patients and others with severe hypertensive disorders in pregnancy will need blood pressure-lowering drugs that are administered directly into the blood through a catheter (tube) in the vein (intravenous). Medications called hydralazine or labetalol are usually used in these circumstances. If there is evidence of seizures or even the potential of seizures, the patient will be put on magnesium . a drug that prevents eclamptic seizures. Depending on the severity of the disease and the maturity of the pregnancy, a pregnant woman may have to be induced into labor early or may need to have an urgent cesarean section to prevent permanent damage to her or the fetus. Patients respond much better if they get aggressive anti-seizure therapy and delivery, if appropriate.

Prevention

There are many risk factors for the development of hypertension in pregnancy. Some of these include:

  • A first or second pregnancy
  • A patient older than 40
  • A very young patient
  • An African American patient
  • Low socioeconomic status
  • Personal or family history of hypertension in pregnancy
  • A different father for this fetus than the previous one
  • Problems with high blood pressure before pregnancy
  • Chronic kidney problems
  • A patient who suffers from diabetes
  • Twin pregnancy

Many of these risk factors cannot be controlled. However, good prenatal care -- always seeing your doctor as scheduled and having your blood pressure checked regularly -- is a way to protect yourself. If you need blood pressure-lowering medications, take them as prescribed. Furthermore, telling your doctor about unusual or severe swelling or sudden weight gain is important. Weight gain of greater than 2 pounds per week is of concern. Symptoms like persistent headache, blurred vision and upper abdominal pain are often present late in the disease process. However, if you have any of these symptoms, you should report them to your doctor immediately.

Summary

In summary, hypertensive disorders of pregnancy are a group of diseases characterized by blood pressures greater than 140/90 in late pregnancy. These disorders include preeclampsia, eclampsia and HELLP syndrome, and are characterized by high blood pressure but also -- depending on severity and type -- pathologic swelling, kidney disease, liver dysfunction, clotting disorders, bleeding in the brain, and other very serious problems. Hypertensive disorders in pregnancy can lead to very severe illness, even death, if not managed appropriately. Multiple medications can be used to manage the high blood pressure, and magnesium can prevent seizures in eclamptic patients. Delivery, however, is the definitive treatment for very severe cases of hypertensive disorders in late pregnancy. You can decrease your risk of getting hypertension in pregnancy or its consequences by getting good prenatal care and taking blood pressure medications if your doctor prescribes them.

Dr. Michelle Finkel is an attending in the Emergency Department of the Massachusetts General Hospital. Dr. Finkel has published articles in emergency medicine journals and contributed to textbooks on a diverse group of topics. Subjects include high blood pressure in pregnancy, headaches, physician professionalism, substance abuse, and abdominal pain.

Copyright © Michelle Finkel. Permission to republish granted to Pregnancy.org, LLC.