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Preeclampsia:
High Blood Pressure in Pregnancy

by Bobbi Kimsey, SNM

Medical University of South Carolina

For centuries, high blood pressure, or hypertension during pregnancy has been one of the leading causes of perinatal mortality (death of mother, fetus or newborn). Pre-eclampsia (or toxemia, as it was historically called) is the hypertensive disease that occurs only in pregnancy. Almost 10 percent of pregnancies are complicated by pre-eclampsia.

Who gets pre-eclampsia?

Pre-eclampsia occurs more often among some groups of women. At higher risk for the disease are women who:

• are under 20 years old, with a first pregnancy, all races
• are over 35 years old, with a first pregnancy, especially minorities
• have chronic, or "essential" hypertension
• had hypertension in a previous pregnancy, other than the first
• have multiple gestation (twins, etc.)
• have diabetes

What are the signs of pre-eclampsia?

Pre-eclampsia has been called the great imitator because its symptoms are often much like many other diseases. Characteristic signs and symptoms occur after the 20th week of pregnancy and include:

1. High Blood Pressure: A BP of at least 140 over 90 is considered hypertension (160 over 110 is "severe"). If the woman's normal (pre-pregnant or very early pregnancy) blood pressure is not known, it's very hard to distinguish pre-eclampsia from chronic hypertension. Pre-eclampsia is more dangerous to the mother and baby. About 20 percent of women with chronic hypertension will develop pre-eclampsia too.
2. Swelling, or "edema": This is a common sign and may go along with a rapid weight gain of greater than 2 lb per week. Swelling is a confusing symptom. It is normal to have some swelling of the feet or ankles, especially late in pregnancy, and some women with pre-eclampsia will have no edema. Swelling is not a reliable symptom of pre-eclampsia.
3. Protein in the urine: The presence of protein in the urine is considered to be an important factor for making the diagnosis of pre-eclampsia. The disease causes damage to the filtering function of the kidneys (repairs itself after delivery), which allows protein to "spill" into the urine. Even though it is a reliable sign of pre-eclampsia, protein in the urine very often does not occur until the disease has progressed to a later stage.

How is Pre-eclampsia different from a normal pregnancy?

Many adjustments in the mother's body happen during a pregnancy to allow the fetus to grow normally, and to help the mother's systems handle the additional "work" required by the pregnancy. Some adjustments do not happen the same way in the woman with pre-eclampsia.

1. In a normal pregnancy the fluid part of the mother's blood increases dramatically, resulting in a 35-50% increase in the total volume. This helps serve the added needs of the uterus and placenta, among other functions. In the woman with pre-eclampsia, the blood volume increases only a small amount or not at all.
2. The "resistance", or stiffness of the blood vessels throughout the mother's body normally decreases, allowing free flow of blood to the placenta and uterus. Pregnancy hormones and changes in the blood vessel regulating mechanisms "relax" the vessel walls. With pre-eclampsia, instead of relaxing, the blood vessels spasm.
3. Normally, the pregnant woman's blood pressure drops a little in mid-pregnancy, partly because of the increase in volume of blood, and partly due to the relaxing of the blood vessels. With pre-eclampsia, the blood pressure does not drop in mid-pregnancy, and the blood pressure increases in the last weeks.
4. With the increase in blood volume and relaxed vessels, the normal pregnant woman gets extra blood flow to the uterus, kidneys, liver and other organs. In the woman with pre-eclampsia, the vessels are in spasm, and this blood flow is decreased instead. The spasm in the small vessels of the body is believed to cause the organ damage that happens with the disease. Kidney damage is one example - protein in the urine is what results from the damage. Other organs, especially the liver can also be damaged. Except in the most severe cases, organ damage heals by itself after delivery of the baby.
5. In the normal pregnancy, blood clotting is affected very slightly. With severe pre-eclampsia, platelets (clotting factors in the blood) can be very low, and the blood does not clot normally. This results in a life threatening risk of internal bleeding.

What can happen to the mother with pre-eclampsia and her baby?

Damage to organs, such as the kidney and liver, and swelling or fluid in the lungs are dangerous complications of pre-eclampsia. These problems are caused by the decreased flow of blood and vessels in spasm. Since the uterus also gets less blood flow, often the placenta is damaged. The baby may not grow well, and may be overly stressed during labor.

Many women with pre-eclampsia will deliver an essentially healthy baby. Some women will experience only an anxious nurse-midwife or doctor, and maybe delivery a week or so earlier. Some women, however, progress rapidly to more severe forms of the disease. Two very serious consequences are:

1. Eclampsia is when the mother has convulsions. Serious complications such as brain injury as a result of the convulsion are uncommon but do occur. The fetus is deprived of oxygen during the convulsion, and damage or separation of the placenta can occur. Preventing eclampsia is one of the major goals of treating pre-eclampsia.
2. HELLP Syndrome stands for hemolysis (destruction of red blood cells), elevated liver enzymes (indicating liver damage), and low platelets (internal bleeding risk). HELLP Syndrome is a life threatening condition for both mother and fetus.

What causes pre-eclampsia?

It is not known what causes this disease. A current theory holds that pre-eclampsia is a process that begins early in the pregnancy as the developing embryo implants in the wall of the uterus to form the placenta. Normally, a complex series of events causes changes in the blood vessels of the uterus which allow them to remain relaxed to nourish the growing baby. In pre-eclampsia, this process does not occur or is incomplete very early. The chemical imbalances that result are believed to lead to the spasm and "stiffness" of the blood vessels throughout the mother's body. It is this spasm that causes the complications of pre-eclampsia - namely organ damage.

How is pre-eclampsia treated?

Delivery of the placenta and baby is the only known treatment. When the disease occurs in the last weeks of pregnancy, bed rest and observation for worsening of pre-eclampsia may be attempted, but often labor must be induced, or in severe cases, cesarean birth performed.

When the disease occurs further from the due date, the risks of premature birth must be weighed against the risks of pre-eclampsia. Generally, the earlier signs of the disease are seen, the more severe it is likely to become. Even with mild pre-eclampsia near full term, however, a significant decrease in placental blood flow has already occurred, and delivery is recommended.

Can pre-eclampsia be prevented?

The search for something to predict or prevent pre-eclampsia has continued since the time of Hippocrates. Most suggestions have not helped much. Considering the current theory of early placenta development problems, it seems unlikely that prevention will be a simple matter.

Among the suggestions, several have involved dietary changes. Calcium intake appears to play some role in reducing pre-eclampsia. Adequate amounts of calcium (1,200 - 1,500 mg per day) can be obtained from a balanced diet which includes 3 to 4 servings of milk or dairy products daily. If the diet is not adequate, a supplement may be recommended.

Low dose aspirin therapy is being studied as one possible way to prevent the chemical imbalances at the placenta, which are believed to be a cause of pre-eclampsia. Currently, the American College of Obstetricians and Gynecologists recommends that aspirin be used only in women at very high risk for pre-eclampsia. There isn't enough evidence of its benefits to recommend it for all pregnant women.

Although the disease may not be prevented, the serious complications from pre-eclampsia can be. The most effective prevention is early and regular prenatal care by a qualified physician, nurse midwife or nurse practitioner. Women can be aware of the danger signs of pre-eclampsia, and report them promptly to their care provider or clinic:

Danger Signs of Pre-eclampsia

1. Severe headache
2. Seeing "spots" or "flashing lights" while at rest
3. Sudden increase in swelling, such as over 2-3 days, especially of the face
4. Abdominal pain
5. Nausea, vomiting, feeling sick

The author gives permission to reproduce this article for the benefit of women, provided it remains complete and unchanged in any way. If links are made to this article from other sites, please notify at webwife@musc.edu.

References

ACOG Technical Bulletin (1994). Management of hypertension in pregnancy. Washington, DC: American College of Obstetricians and Gynecologists.

Cunningham, F. G., et. al. (1993). Williams Obstetrics. 19th Edition. Norwalk, Connecticut: Appleton and Lange, 763-817.

Roberts, J. (1994). Current perspectives on preeclampsia. Journal of Nurse-Midwifery, 39(2), 70-90.

Sibai, B. M. (1988). Pitfalls in diagnosis and management of preeclampsia. American Journal of Obstetrics and Gynecology, 159, 1-5.

Pregnancy Information
Pregnancy, Birth and Women's Health Information
MUSC Nurse-Midwifery Homepage

May 1996

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