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pregnancy induced hypertension pregnancy and high
blood pressure
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High Blood Pressure During
Pregnancy 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 hypertension.
Up to 5 percent of women have hypertension before they become
pregnant.1 This is called chronic
hypertension. Another 5 to 8 percent develop hypertension during
pregnancy.2 This is referred to as gestational hypertension. Gestational hypertension
generally goes away soon after delivery; however, women who develop it may be at increased risk of
developing hypertension later in life.
High blood pressure usually causes no noticeable symptoms,
whether or not a woman is pregnant. However, hypertension during pregnancy can cause serious
complications for mother and baby. Fortunately, serious problems usually can be prevented
with proper prenatal care.
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How is blood pressure measured?
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A pregnant woman’s blood pressure is measured at each prenatal visit. The
health care provider measures blood pressure with an inflatable cuff that wraps
around the 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 with one or more additional readings
to determine if a woman truly has high blood pressure
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What is chronic hypertension?
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Chronic
hypertension is defined as high blood pressure that is diagnosed before pregnancy or
before the 20th week of pregnancy. This form of hypertension does not go away after
delivery.
The causes of chronic hypertension are not thoroughly understood,
although heredity, diet and lifestyle are believed to play a role. Untreated hypertension can
increase the risk of serious health problems such as heart attack and stroke.
Women with chronic hypertension should see their health care provider
before attempting to conceive. A pre-pregnancy 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 a group of drugs called angiotensin-converting-enzyme (ACE) inhibitors—can
harm the fetus. Some women with chronic hypertension 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.
Most women with chronic hypertension have healthy pregnancies.
However, about 25 percent develop a form of gestational
hypertension called preeclampsia (see below), which poses special
risks.2,3
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What is gestational hypertension?
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There are
two main forms of gestational hypertension. Both occur after the 20th week of pregnancy and
go away without treatment soon after delivery. Preeclampsia is a potentially serious
disorder, which is characterized by high blood pressure and protein in the urine.
When high blood pressure is not accompanied by protein in the
urine, it is referred to as gestational hypertension. However, gestational hypertension may
progress to preeclampsia, so all women who develop high blood pressure in pregnancy are monitored
closely.
Preeclampsia also may be accompanied by swelling (edema) of the hands and face and sudden weight
gain (5 or more pounds in one week). Other signs of preeclampsia include blurred vision, severe
headaches, dizziness and intense stomach pain. A pregnant woman should contact her health care
provider right away if she develops any of these symptoms.
Preeclampsia usually occurs after about 30 weeks of
pregnancy. Most cases are mild, with blood pressure around 140/90. Women with mild
preeclampsia often have no obvious symptoms. If left untreated, though, preeclampsia can
cause serious problems.
It’s important to remember that many women who develop preeclampsia or gestational hypertension do
so at term (at or beyond 37 weeks of gestation). These women generally have few complications.
What risks do preeclampsia
and other forms of hypertension pose for a pregnant woman and her
fetus?
All forms of hypertension can constrict the blood vessels in the uterus that supply the fetus
with oxygen and nutrients. When this occurs before term, it can slow the fetus’s growth,
sometimes resulting in low birthweight.
Hypertension also increases the risk of pretermdelivery (before 37 weeks gestation).
Premature and low-birthweight babies face an increased risk of health problems during the
newborn period and lasting disabilities, such as learning problems and cerebral
palsy.
Women with hypertension also have an increased risk of placental
abruption, which is separation of the placenta 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. While all women
with high blood pressure during pregnancy face some increased
risk of abruption and the other complications discussed above, the risk is greatest in women
who have preeclampsia along with chronic high blood pressure.3
Preeclampsia also can quickly progress to a rare but life-threatening
condition called eclampsia, causing seizures and sometimes coma. Fortunately, eclampsia is rare in
women who receive regular prenatal care. At each prenatal visit, blood pressure is measured and urine is checked for
protein, so that preeclampsia can be diagnosed and treated before it can progress to
eclampsia.
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How is preeclampsia treated?
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The only cure
for preeclampsia is delivery. However, this is not always best for the baby. So treatment depends
upon how severe the problem is and how far along a woman is in her pregnancy. If a woman is at term
(37 to 40 weeks), the preeclampsia is mild, and her cervix has begun to thin and dilate (signs that
it’s ready for delivery), her health care provider probably will recommend inducing labor. This
prevents any potential complications that could develop if the pregnancy continues and the
preeclampsia worsens. If her cervix is not yet ready for labor, her provider may recommend
medication to help prepare her cervix for induction or continue to monitor her and her baby closely
until labor starts on its own.
If a woman develops mild preeclampsia before her 37th week, her
provider probably will recommend that she reduce her activities. In some cases,
hospitalization may be recommended, though most women can be treated at home. Her baby’s well-being
will be closely monitored with tests such as ultrasound and fetal heart rate monitoring.
Blood tests probably will be recommended for the
pregnant woman to see if the preeclampsia is progressing and harming her health.
If a woman has severe preeclampsia, she should be hospitalized. Her
health care provider will probably recommend inducing labor if she is beyond 33 to 34 weeks
gestation.4At this stage of pregnancy, the risk of prematurity is generally
outweighed by the risk of progression to
eclampsia. Before inducing labor, doctors 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 to
reduce the risk of prematurity-related problems. A woman who develops severe preeclampsia at
less than 32 weeks gestation sometimes can be monitored closely in the hospital, to prolong
the pregnancy safely while her baby matures.
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. Babies born early may have difficulties due to prematurity, such as
trouble breathing. Most of these infants will do better in an intensive care nursery than if
they had stayed in the uterus.
About 10 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.5Symptoms may include
nausea and vomiting, headache, upper abdominal pain and general malaise. Women with HELLP
syndrome, which also can develop in the first 48 hours after delivery, 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.
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How are women with gestational hypertension and
chronic hypertension treated?
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Most of these women have
successful pregnancies. Their health care providers monitor their blood pressure and urine carefully for signs of
preeclampsia or worsening hypertension. Tests such as ultrasound and fetal heart rate testing
may be recommended to check on fetal growth and well-being. If tests are normal, they may not
need to be repeated unless the mother’s condition changes. The provider may recommend that
the pregnant woman cut back on her activities and avoid aerobic exercise.
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Can a woman with preeclampsia have a vaginal
delivery?
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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.
Women with severe preeclampsia or eclampsia generally are treated
with a drug called magnesium sulfate to help prevent seizures during labor and delivery. It is less
clear whether women with mild preeclampsia benefit from this drug.
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What causes preeclampsia and who is at
risk?
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Doctors do not know what causes preeclampsia. However, women are more
susceptible if they have any of these risk factors1,3:
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First
pregnancy
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Family history of
preeclampsia
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Personal history of chronic
high blood pressure, kidney disease, diabetes,
systemic lupus erythematosus (a disease often characterized in its early stages
by arthritis-like stiffness, a butterfly-shaped rash across the nose and cheeks,
fatigue and weight loss), and certain
thrombophilias
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Multiple
pregnancy
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Age less than 20 years, or over
35
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African-American
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Higher than normal
weight
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Personal history of
preeclampsia
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Is preeclampsia likely to recur in another
pregnancy?
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Women who have had preeclampsia are more susceptible to developing it
again in another pregnancy. The risk of recurrence appears to be highest when preeclampsia has occurred before the
29th week of gestation and, in some cases, may be as high as 65 percent in another
pregnancy.5 About 20 percent of women who have developed
preeclampsia after the 37th week of pregnancy develop it
again.5
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Can preeclampsia and gestational hypertension be
prevented?
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Currently, there is no way to prevent preeclampsia or gestational
hypertension. However, a 1999 British study suggested that some high-risk women (including women who had
preeclampsia in a previous pregnancy) may be able to reduce their risk of preeclampsia by
taking vitamins C and E through the second half of pregnancy.6The high-risk women who took the vitamins reduced
their risk of developing preeclampsia by about 75 percent. The researchers caution that
more studies are needed before this treatment can be widely recommended. Other treatments
that looked promising in early studies (such as aspirin and calcium) have not proven helpful
in preventing preeclampsia.
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. Another grantee
has been investigating whether certain fatty acids found in fish, such as salmon and
mackerel, may help reduce the risk of preeclampsia.
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