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Patient information: Preeclampsia (Beyond the Basics)

Vanessa A Barss, MD, FACOG
John T Repke, MD
Section Editor
Charles J Lockwood, MD, MHCM
Deputy Editor
Vanessa A Barss, MD, FACOG
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There are four major types of high blood pressure that may occur during pregnancy:


Chronic hypertension

Preeclampsia superimposed upon chronic hypertension

Gestational hypertension (also called transient hypertension)

This topic will review high blood pressure related to preeclampsia, the treatment of preeclampsia, and the possible complications of preeclampsia.


Many women with preeclampsia have smaller than normal blood vessels feeding the placenta. Abnormalities in the development of these blood vessels very early in pregnancy appear to initiate a cascade of events that eventually cause high blood pressure (hypertension) and the other signs and symptoms of the disease. However, why this happens to some women and not others is not completely understood.

Most women with preeclampsia gradually develop hypertension and excess protein in the urine (proteinuria). Some women develop hypertension and other signs of the disease without developing proteinuria. Signs of preeclampsia can appear anytime during the last half of pregnancy (after 20 weeks of pregnancy) or in the first few days postpartum, and typically resolve within a few days after delivery.

Preeclampsia is sometimes called by other names, including toxemia, pregnancy-induced hypertension, and preeclamptic toxemia. It is mild in most cases. One severe form of preeclampsia is called HELLP syndrome (H = hemolysis, EL = elevated liver enzymes, LP = low platelets). A woman is said to have eclampsia if she has one or more seizures and has no other conditions that could have caused the seizure.

In the United States, preeclampsia occurs in 3 to 4 percent of pregnancies. Most cases occur at or near term (after 37 weeks of pregnancy), although 10 percent of cases occur before 34 weeks of pregnancy.

Chronic hypertension — Chronic hypertension is defined as a blood pressure ≥140/90 mmHg diagnosed before pregnancy, before the 20th week of pregnancy, or that persists more than 12 weeks after delivery.

Chronic hypertension with superimposed preeclampsia — This term describes a woman with chronic hypertension who develops signs of preeclampsia after the 20th week of pregnancy.

Gestational hypertension — Women with gestational hypertension have all of the following:

Blood pressure ≥140/90 mmHg

No protein in the urine (proteinuria)

Pregnancy duration of at least 20 weeks

No previous history of high blood pressure.

Over time, some pregnant women with gestational hypertension will develop proteinuria or other signs of preeclampsia and be considered preeclamptic, while others will be diagnosed with chronic hypertension because of persistently high blood pressure after delivery.


There are no tests that can reliably predict who will get preeclampsia, and there is no way to completely prevent it. Women with one or more of the following characteristics have an increased risk of developing preeclampsia:

First pregnancy (excluding miscarriages)

High blood pressure, kidney disease, lupus, or diabetes prior to pregnancy

Gestational diabetes

Multiple gestation (eg, twins or triplets)

A family history of preeclampsia in a sister or mother

A previous history of preeclampsia

Age under 20 years and possibly age over 35 to 40 years


Conversely, women who do not develop preeclampsia in their first pregnancy are at low risk of developing it in a subsequent pregnancy.

Doctors may recommend that women who have risk factors that place them at high risk of developing preeclampsia take low-dose aspirin starting in the late first trimester and continuing into the third trimester of pregnancy to reduce this risk [1]. Examples of high-risk women include women with a history of early onset preeclampsia with delivery before 34 weeks of gestation or preeclampsia in more than one pregnancy. Low-dose aspirin is not recommended for women at low or average risk of developing preeclampsia.


Signs and symptoms of preeclampsia occur, in part, due to changes inside the small arteries that decrease blood flow to major maternal organs such as the kidney, brain, and liver, as well as the placenta.

Maternal — Most women with preeclampsia never experience anything more than mild high blood pressure and a small amount of excess protein in the urine. These changes do not cause symptoms; therefore, prenatal visits to check blood pressure and measure urinary protein are scheduled frequently in the last half of pregnancy.

Signs of severe disease — Preeclampsia can worsen and develop features of severe disease. This usually occurs over several days to weeks, but may occur more quickly. Severe features of preeclampsia consist of one or more of the following signs or symptoms. However, the symptoms may be subtle, and patients should not hesitate to mention any concerns about possible symptoms of preeclampsia to their provider:

Symptoms of severe disease:

Persistent severe headache

Visual problems (blurred or double vision, blind spots, flashes of light or squiggly lines, loss of vision)

New shortness of breath (due to fluid in the lungs)

Pain in the mid- or right-epigastrium (similar to heartburn)

Signs of severe disease:

Blood pressure ≥160/110 mmHg. Women with blood pressures in this range have an increased risk of stroke.

Abnormal kidney tests (eg, serum creatinine >1.1 mg/dL)

Low platelet count

Liver abnormalities (detected by blood tests)

Pulmonary edema (fluid in the lungs)

Fetal — Blood flow to the placenta carries oxygen and nutrients from mother to baby. Preeclampsia can reduce blood flow to the placenta, which can the following effects on the baby:

Abnormal nonstress test or biophysical profile score (see 'Fetal monitoring' below)

Slowed growth of the baby, based upon an ultrasound

Decreased amount of amniotic fluid around the baby, noted on ultrasound

Decreased blood flow through the umbilical cord, noted on Doppler tests (performed during ultrasound).


The only cure for preeclampsia is delivery of the baby and placenta. Although bedrest and taking high blood pressure medication can lower blood pressure and thus reduce the risk of stroke, these treatments do not improve the abnormalities in the mother's blood vessels and prevent progression of the disease.

At term — Pregnancies complicated by preeclampsia without severe features (formerly mild preeclampsia) are delivered at 37 weeks (ie, term) because delivery is the most effective treatment for preeclampsia. This helps to minimize the risk of harm to the woman or her baby from worsening preeclampsia. Babies at or near term are not at high risk of complications from prematurity and usually will not need to spend time in a special care nursery.

Before term — If preeclampsia occurs before term and there are no severe features of the disease, it may be possible to delay delivery to allow the baby more time to grow and mature, while monitoring the woman and baby closely. If severe features of preeclampsia occur before term, delivery is often necessary to prevent complications in the woman or her baby. In the setting of preeclampsia with severe features, if both the maternal and fetal statuses are reassuring then delivery can be delayed up to but not beyond 34 weeks.

The method of delivery (vaginal or cesarean birth) depends upon a number of factors, such as the position of the baby, the dilation and effacement (thinning) of the cervix, and the baby's condition. In most situations, vaginal delivery is possible.

Steroids — Babies delivered prematurely are at risk for breathing problems because their lungs may not be fully developed. Women who are likely to require preterm delivery (at or before 34 weeks of pregnancy) are usually given two steroid injections (eg, betamethasone) to speed fetal lung development. The steroids also decrease other potential complications of preterm birth, such as intraventricular hemorrhage (bleeding into the brain). The two injections are given 24 hours apart, and the full benefit of the treatment occurs 48 hours after the first injection. A second course of steroids may be needed if more than a few weeks have passed from the initial course and delivery becomes necessary, and provided that an additional delay of delivery for 24 to 72 hours is medically appropriate.

Maternal monitoring — When delivery is delayed, the mother and baby will be monitored. The woman may be admitted to the hospital or may be allowed to stay at home and have frequent office visits. Women who are at home should call their healthcare provider immediately if any symptoms of severe disease develop (see 'Maternal' above).

Maternal monitoring usually includes blood pressure measurements and blood and urine tests to check liver and kidney function, and platelet counts.

Fetal monitoring — Fetal monitoring includes a combination of nonstress tests and ultrasound examination.

Non-stress testing is performed to monitor the baby's condition. It is done by measuring the baby's heart rate with a small device that is placed on the mother's abdomen. The device uses sound waves (ultrasound) to measure the baby's heart rate over time, usually for 15 to 30 minutes. Normally, the baby's baseline heart rate should be between 120 and 160 beats per minute. Normally, an increased rate should occur periodically; the increase should be at least 15 beats per minute above the baseline heart rate for 15 seconds. The test is considered reassuring if two or more fetal heart rate increases are seen within a 20 minute period. Further testing may be needed if these increases are not observed after monitoring for 40 minutes. In general, outpatients undergo fetal testing twice per week, while inpatient testing is often performed daily.

Ultrasound is used to monitor the baby's growth, assess its well-being, and evaluate blood flow through the umbilical cord (called a Doppler test). A biophysical profile assesses well-being by using ultrasound to evaluate the baby's movements, breathing activity, movement of the arms and legs, and amniotic fluid volume.

Induced labor — If the mother or baby's test results are concerning, the healthcare provider will usually recommend delivery. The most common reasons for delivery in women with preeclampsia are listed the table (table 1):

If the cervix is still closed and long, medications may be applied directly to the cervix to help it open and thin. Most women will also require an intravenous medication, oxytocin (Pitocin), to stimulate the uterus to contract. If labor does not progress with these measures, or if complications develop that require the baby to be delivered quickly, a cesarean birth is usually performed. (See "Patient information: C-section (cesarean delivery) (Beyond the Basics)".)

Preventing seizures — Because women with preeclampsia can develop eclampsia (seizures), most patients are treated with an anticonvulsant medication. Intravenous (IV) magnesium sulfate is the drug most commonly used to prevent seizures. Dietary supplements that contain magnesium are not effective or recommended for prevention of seizures. IV magnesium is safe, although high blood levels of magnesium can be harmful. The mother and baby are monitored closely during treatment. Magnesium is given to the woman during labor and usually for 24 hours after delivery.

Severe hypertension is treated with one or more IV high blood pressure medications to lower the risk of a maternal stroke.


High blood pressure and protein in the urine resolve after delivery, usually within a few days. Severe hypertension should be treated, and some women will require a high blood pressure medication after being discharged from the hospital. This can be discontinued when the blood pressure returns to normal levels, usually within six weeks. Your provider may recommend monitoring of blood pressure after discharge from the hospital either at his/her office or at home, and again in about 10 to 14 days to confirm resolution of hypertension. Avoiding nonsteroidal antiinflammatory drugs (NSAIDs) for pain relief may help control persistent hypertension, as these drugs may adversely affect blood pressure and kidney function.

Blood pressure that continues to be elevated beyond 12 weeks after delivery is unlikely to be related to preeclampsia and may require long-term treatment. (See "Patient information: High blood pressure treatment in adults (Beyond the Basics)".)


Mildly elevated blood pressure over a few weeks or months is not usually harmful; it does not have the same long-term risks (stroke, heart attack) as chronic high blood pressure. Losing protein in the urine due to preeclampsia does not damage the kidneys. In women with mild features of preeclampsia near term, newborn outcomes are generally good.

Preeclampsia with severe features can cause temporary abnormalities in the woman's liver and kidney function and a low platelet count (thrombocytopenia, which can be associated with bleeding). In women with severe features of the disease, especially those who are preterm, preterm delivery may be required, leading to neonatal problems related to prematurity. (See "Short-term complications of the premature infant".)

Women who have preeclampsia with severe features that develop before term, recurrent preeclampsia, or gestational hypertension appear to be at increased risk of cardiovascular disease later in life, including during the premenopausal period.


Most women who experience preeclampsia will not have it in a subsequent pregnancy. The risk of recurrent preeclampsia is between 5 and 70 percent.

Women who developed severe features of preeclampsia and were delivered before 30 weeks gestation having the highest risk (up to 70 percent) of preeclampsia in future pregnancies.

Women with preeclampsia without severe features of the disease near term have only a 5 percent chance of developing it again.


Women with preeclampsia develop high blood pressure (greater than 140/90 mmHg) and generally have protein in their urine, although some women develop other features of the disease without proteinuria. This can occur anytime during the last half of pregnancy (after 20 weeks of gestation) or in the first few days after delivery.

Preeclampsia occurs in 3 to 4 percent of pregnancies in the United States. It is not known why some women develop preeclampsia while others do not. Currently, there are no tests that can reliably predict who will get the disease, and there is no way to completely prevent it. Taking low-dose aspirin in the late first trimester through the third trimester appears to lower the risk of developing preeclampsia in women at high risk of developing the disease.

The majority of women with preeclampsia have no symptoms. The disease can worsen and develop severe features characterized by the following signs and symptoms (table 2).

A pregnant woman should immediately call her healthcare provider if any of the signs or symptoms of severe disease develop, or if she has decreased fetal activity, vaginal bleeding, abdominal pain, or frequent uterine contractions.

The only cure for preeclampsia is delivery of the baby and placenta. Reduced physical activity, but not strict bed rest, and taking high blood pressure medication can lower the blood pressure but will not stop preeclampsia from worsening or reduce the risk of its complications.

If tests monitoring the mother’s or baby's condition show concerning results, the healthcare provider may recommend delivery. A vaginal delivery is often possible.

Because women with preeclampsia can develop seizures (called eclampsia), most women are treated with an anticonvulsant medication. Magnesium sulfate is the drug most commonly used to prevent seizures. It is safe for both mother and baby. It is given intravenously to the mother during labor and usually for 24 hours after delivery.

High blood pressure and protein in the urine resolve after delivery, usually within a few days. However, some women require medication to reduce high blood pressure after being discharged from the hospital.

Most women who experience preeclampsia without severe features will not have it in a future pregnancy. The risk of recurrence is higher in women with severe features of preeclampsia, especially when they occur in the second trimester.

Women who develop preeclampsia appear to be at increased risk of developing cardiovascular disease later in life, so regular health care may be particularly important in this group of patients.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient information: Preeclampsia (The Basics)
Patient information: Swelling (The Basics)
Patient information: High blood pressure and pregnancy (The Basics)
Patient information: HELLP syndrome (The Basics)
Patient information: Having twins (The Basics)
Patient information: Prenatal care (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient information: C-section (cesarean delivery) (Beyond the Basics)
Patient information: High blood pressure treatment in adults (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Acute kidney injury (acute renal failure) in pregnancy
Preeclampsia: Clinical features and diagnosis
Critical illness during pregnancy and the peripartum period
Expectant management of preeclampsia with severe features
Gestational hypertension
Headache in pregnant and postpartum women
HELLP syndrome
Hematologic changes in pregnancy
Management of hypertension in pregnant and postpartum women
Preeclampsia: Management and prognosis
Preeclampsia: Pathogenesis
Prediction of preeclampsia
Preeclampsia: Prevention
Short-term complications of the premature infant

The following organizations also provide reliable health information.

National Library of Medicine


The Mayo Clinic



Literature review current through: Jul 2015. | This topic last updated: Sep 25, 2014.
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