Blood pressure is the force of the blood pushing against the walls of the arteries (blood vessels that carry oxygen-rich blood to all parts of the body). When the pressure in the arteries becomes too high, it is called high blood pressure or hypertension.
About 8 percent of women have problems with high blood pressure during pregnancy (1). There are several types of high blood pressure that affect pregnant women. Some types start before pregnancy, and others develop during pregnancy. All types of high blood pressure can pose risks to the pregnant woman and her baby. Fortunately, problems usually can be managed with proper prenatal care.
How is blood pressure measured?
At each prenatal visit, the health care provider measures blood pressure with an inflatable cuff that wraps around the woman’s upper arm. The pressure in the arteries is measured as the heart contracts (systolic pressure) and when the heart is relaxed between contractions (diastolic pressure).
The blood pressure reading is given as two numbers, with the top number representing the systolic and bottom number the diastolic pressure (for example, 110/80). A systolic reading of 140 or higher, or a diastolic reading of 90 or higher, is considered high blood pressure. Because blood pressure can go up and down during the day, health care providers often re-check a high reading to determine if a woman truly has high blood pressure.
What forms of high blood pressure occur in pregnancy?
There are four main forms of high blood pressure in pregnancy:
- Preeclampsia: This potentially serious disorder is characterized by high blood pressure and protein in the urine. It usually develops after the 20th week of pregnancy and goes away after delivery.
- Gestational hypertension: This form of high blood pressure develops after the 20th week of pregnancy and goes away after delivery. Affected women do not have protein in the urine. However, some women with gestational hypertension develop preeclampsia later in pregnancy.
- Chronic hypertension: This is high blood pressure that is diagnosed before pregnancy or before the 20th week of pregnancy. It does not go away after delivery.
- Chronic hypertension with preeclampsia: About 25 percent of women with chronic hypertension also develop preeclampsia (1, 2).
What are the symptoms of preeclampsia and other forms of high blood pressure?
Most pregnant women with mild preeclampsia and other forms of high blood pressure have no symptoms. In order to detect these cases, providers measure a woman’s blood pressure and check her urine for protein at each prenatal visit. More severe cases of preeclampsia may be accompanied by:
- Severe headaches
- Vision problems (blurriness, flashing lights, sensitivity to light)
- Pain in the upper right abdomen
- Sudden weight gain (5 or more pounds in one week) with fluid retention in the legs and puffiness of the face
A pregnant woman should contact her health care provider right away if she develops any of these symptoms.
Most cases of preeclampsia are mild, with blood pressure around 140/90. However, even these cases must be properly managed to make sure the condition doesn’t worsen and cause serious problems.
What risks do preeclampsia and other forms of high blood pressure pose for a pregnant woman and her fetus?
Without treatment, severe preeclampsia can damage a woman’s kidneys, liver and brain. All forms of high blood pressure increase the risk for pregnancy complications. However, the risk of complications is highest in women with chronic high blood pressure accompanied by preeclampsia (1):
- Low birthweight: High blood pressure can constrict the blood vessels in the uterus. This can affect the supply of oxygen and nutrients to the placenta, which nourishes the fetus. When this occurs before term, it can slow the fetus’s growth, sometimes resulting in the birth of a low-birthweight baby (less than 5½ pounds).
- Premature delivery (before 37 completed weeks of pregnancy): Some women develop severe high blood pressure or other symptoms of worsening preeclampsia, despite treatment. Some of these women may require early delivery to prevent severe complications to mother and baby, sometimes resulting in the birth of a premature and low-birthweight baby. These babies are at increased risk for health problems during the newborn period and lasting disabilities, such as learning problems and cerebral palsy.
- Placental abruption: The placenta separates partially or completely from the uterine wall before delivery. Severe abruption can cause heavy bleeding and shock, which are dangerous for both mother and baby. The most common symptom of abruption is vaginal bleeding after 20 weeks of pregnancy. A pregnant woman always should report any vaginal bleeding to her health care provider immediately.
Preeclampsia can quickly progress to a life-threatening condition called eclampsia, causing seizures and, sometimes, coma. Fortunately, eclampsia is rare in women who receive regular prenatal care.
How is preeclampsia managed?
Treatment depends upon how severe the problem is and how far along a woman is in her pregnancy. Women who develop mild preeclampsia at term (at or beyond 37 weeks of gestation) generally have few complications. However, the provider may recommend inducing labor to prevent any potential complications to mother or baby if the pregnancy continued and preeclampsia worsened.
If a woman develops mild preeclampsia before her 37th week, her provider usually recommends that she reduce her activities. In some cases, hospitalization may be recommended, though most women are able to stay at home. The baby’s well-being can be closely monitored with tests, such as ultrasound and fetal heart rate monitoring. Blood tests usually are recommended for the pregnant woman to see if the preeclampsia is progressing and harming her health.
Women with severe preeclampsia are hospitalized. The health care provider usually recommends inducing labor if the woman is beyond about 34 weeks gestation (3). At this stage of pregnancy, the risk of prematurity may be outweighed by the risk of serious complications, including eclampsia. Before inducing labor, providers generally treat women who are at less than 34 weeks gestation with a drug called a corticosteroid that helps speed maturity of the fetal lungs. A woman who develops severe preeclampsia at less than 34 weeks gestation sometimes can be monitored closely in the hospital.
Sometimes a woman’s blood pressure continues to rise despite treatment with blood pressure medications, and her baby must be delivered early to prevent serious health problems in the mother, such as stroke, liver damage and seizures. Some women may require a cesarean delivery. Babies born early may have difficulties due to prematurity, such as trouble breathing. Most of these infants do better in an intensive care nursery than they would have if they had stayed in the uterus.
About 20 percent of women with severe preeclampsia also develop a disorder called HELLP (an acronym for hemolysis, elevated liver enzymes, and low platelet count) syndrome, which is characterized by blood and liver abnormalities (4). Symptoms may include nausea and vomiting, headache, upper abdominal pain and general malaise. Women with HELLP syndrome can develop these symptoms during pregnancy or in the first 48 hours after delivery. They are treated with medications to control blood pressure and prevent seizures, and sometimes with blood transfusions. Women who develop HELLP syndrome during pregnancy almost always require early delivery to prevent serious complications.
How are women with gestational hypertension and chronic hypertension treated?
Most of these women have healthy pregnancies. Health care providers monitor their blood pressure and urine carefully for signs of preeclampsia or worsening hypertension. Ultrasound and fetal heart rate testing may be recommended to check on fetal growth and well-being. The provider may recommend that the pregnant woman cut back on her activities and avoid aerobic exercise.
Women with chronic high blood pressure should see their health care provider before attempting to conceive. A preconception visit allows the provider to ensure that the blood pressure is under control and to evaluate any medication the woman takes to control her blood pressure. While some medications to lower blood pressure are safe during pregnancy, others—including angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers—can harm the fetus (2). Some women with chronic high blood pressure may be able to stop taking their medication or reduce their dose, at least during the first half of pregnancy, as blood pressure tends to fall during this time. However, blood pressure needs to be monitored carefully during this period.
Can a woman with preeclampsia have a vaginal delivery?
A vaginal delivery is preferable to a cesarean for a woman with preeclampsia because it avoids the added stresses of surgery. It generally is appropriate for women with preeclampsia to have epidural anesthesia for pain relief during labor and delivery (4).
Women with severe preeclampsia or eclampsia generally are treated with a drug called magnesium sulfate to help prevent seizures during labor and delivery, and during the first 48 hours after delivery. It is less clear whether women with mild preeclampsia benefit from this drug (5).
What causes preeclampsia and who is at risk?
The causes of preeclampsia are not completely understood. It appears that placental abnormalities, genetic and immune factors and environmental exposures all may contribute (6). Studies show that women are more likely to develop preeclampsia if they have any of these risk factors (1, 4):
- First pregnancy
- Family history of preeclampsia
- Personal history of chronic high blood pressure, kidney disease, diabetes, certain thrombophilias (blood-clotting disorders), systemic lupus erythematosus and other autoimmune disorders
- Multiple pregnancy
- Age less than 20 years, or over 35
- African-American
- Higher-than-normal weight
- Personal history of preeclampsia
Is preeclampsia likely to recur in another pregnancy?
Women who have had preeclampsia are more susceptible to developing it again in another pregnancy. The earlier in pregnancy a woman develops preeclampsia, the higher her risk appears to be in another pregnancy.
A recent study suggests that the likelihood that preeclampsia will recur is about 40 percent for women who deliver at less that 28 weeks gestation due to preeclampsia, compared to about 13 percent for those who develop preeclampsia at term (7). This study also found that women who are overweight are more likely to develop preeclampsia in another pregnancy than women of normal weight.
Do preeclampsia and other forms of high blood pressure affect a woman’s health later in life?
Studies suggest that women who develop preeclampsia before term may be at increased risk for cardiovascular (heart and blood vessel) disease later in life, especially after menopause (6). Untreated chronic hypertension also increases the risk for cardiovascular disease. Women who have had these disorders should discuss with their health care providers what they can do to reduce their risk.
Can preeclampsia and gestational hypertension be prevented?
Currently, there is no way to prevent preeclampsia or gestational hypertension.
Does the March of Dimes fund research on preeclampsia and other forms of high blood pressure in pregnancy?
The March of Dimes has supported a number of studies aimed at improving understanding of the causes of preeclampsia and at improving treatment for this and other types of high blood pressure in pregnancy. Recent grantees have been seeking to identify genes that may play a role in preeclampsia to identify susceptible women earlier in pregnancy and, ultimately, devise ways to prevent this disorder. Others are developing blood and urine tests that can identify women at high risk for preeclampsia in order to provide early treatment.
Where is additional information on preeclampsia available?
For additional information, contact the Preeclampsia Foundation.
References
- Roberts, J.M., et al. Summary of the NHLBI Working Group on Research on Hypertension During Pregnancy. Hypertension, volume 41, March 2003, pages 437-445.
- Podymow, T., August, P. Update on the Use of Antihypertensive Drugs in Pregnancy. Hypertension, published online 2/7/08, http://hyper.ahajournals.org.
- Sibai, B.M. Diagnosis and Management of Gestational Hypertension and Preeclampsia. Obstetrics and Gynecology, volume 102, number 1, July 2003, pages 181-192.
- American College of Obstetricians and Gynecologists (ACOG). Diagnosis and Management of Preeclampsia and Eclampsia. ACOG Practice Bulletin, number 33, January 2002.
- Scott, J.R. Preventing Eclampsia: Magnesium Sulfate Regimens Revisited. Obstetrics and Gynecology, volume 108, number 4, October 2006, pages 824-825.
- Ilekis. J.V., et al. Preeclampsia—A Pressing Problem: An Executive Summary of a National Institute of Child Health and Human Development Workshop. Reproductive Sciences, volume 14, number 6, September 2007, pages 508-523.
- Mostello, D., et al. Recurrence of Preeclampsia: Effects of Gestational Age at Delivery of the First Pregnancy, Body Mass Index, Paternity, and Interval Between Births. American Journal of Obstetrics and Gynecology, published online 2/14/08, www.ajog.org.
April 2008
