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Pregnant Women Face Increased Risk of Heart Attack

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Duke Health News 919-660-1306

DURHAM, N.C. -- Pregnancy increases a woman's risk of
suffering a heart attack, and the threat is even higher for
women over age 35, according to a recent study conducted by
researchers at Duke University Medical Center. Merely being
pregnant increase a woman's risk three- to four- fold, and
other factors, such as age, smoking or high blood pressure
drive the likelihood higher, they found.

The researchers said their findings suggest
obstetrician/gynecologists should now consider heart attack as
a possible diagnosis when treating pregnant women with chest
pains. They also urged women attempting to become pregnant to
take steps to prevent heart attacks by lowering their blood
pressure, stopping smoking and attaining a healthy weight.

The researchers emphasize that heart attacks, or myocardial
infarctions, during pregnancy are rare, occurring in roughly
six out of every 100,000 women. However, physicians have not
previously appreciated how dramatically pregnancy increases the
risk, said Andra James, M.D., MPH, assistant professor of
Obstetrics and Gynecology in Duke's Division of Maternal and
Fetal Medicine.

The research findings were published in the March 28, 2006,
issue of Circulation. The study was funded in part by the
National Institutes of Health.

"Until now, ob/gyns haven't worried about heart attack in
pregnancy because women were not old enough for it to be a
concern," said James, lead study author. "But, that's changing
now because more and more women over ages 35 and 40 are getting
pregnant."

Between 2002 and 2003, the birth rate for women ages 35 to
39 rose 6 percent, and it jumped 5 percent for women ages 40 to
44, James said. The birth rate for 40-to-44-year-old women has
doubled since 1981, according to a 2001 National Vital
Statistics Report.

For their study, the researchers analyzed data on nearly
12.6 million deliveries from 2000 to 2002 through the
Nationwide Inpatient Sample from the Agency for Healthcare
Research and Quality. Of those deliveries, there were 859 heart
attacks – 626 occurred during pregnancy, including during
delivery, and 233 occurred postpartum. Approximately 5 percent
of women died after experiencing a heart attack during
pregnancy.

This research is the first of its kind to analyze a national
sample of pregnant women, enabling researchers to identify more
factors that increase the likelihood of heart attack during
pregnancy, as well as to determine the extent to which
previously suspected factors heighten the danger, James
said.

Between the ages of 20 and 40, a woman's risk of suffering a
heart attack during pregnancy increases by 30 fold. The
increase is gradual, and, based on study analysis, the elevated
risk is actually noticeable in women after age 30.
Thirty-year-old women face a seven-fold increase in their
chances of having a heart attack when compared to a
20-year-old. Older women could be more prone to heart attacks
because of the existence of greater atherosclerosis and their
heart's decreased capacity to handle the stress of pregnancy,
James said.

Race and ethnicity play a large role in determining a
woman's risk of heart attack during pregnancy, the researchers
found. African-American women are more than 50 percent more
likely to have a heart attack than white women, James said.
African-American women over age 35 faced a five-fold spike in
their risk compared to a white woman under age 35 – a
previously unknown finding. According to study data, among
35-year-olds, black women had nearly 41 heart attacks for every
100,000 deliveries, compared to nearly 15 per 100,000 for
Hispanic women and 22.5 per 100,000 for whites.

"African-American women tend to suffer more from high blood
pressure," James said. "This chronic condition puts them at a
greater risk for a heart attack during pregnancy."

James' group identified several other risk factors for heart
attack, including smoking and transfusion. Prior to this
research, physicians did not have enough information to fully
assess the role smoking played in pregnancy-related heart
attacks, the researchers said. The large patient volume in this
study revealed that smoking increases the chances of an
occurrence by eight-fold – a risk equivalent to that produced
by smoking while using oral contraceptives. The increased
levels of estrogen and progesterone in pregnancy (much like
those induced by oral contraceptives) react with chemicals
found in cigarettes and compound the heart attack risk, they
said.

Although transfusions affect only 1 percent of pregnant
women and are mostly a life-saving procedure, the likelihood of
a heart attack jumps seven times in women who require them, the
researchers said.

Other factors that raised risk were hypertension,
thrombophilia, diabetes mellitus, postpartum infection and
migraines, James and her colleagues found.

Even though patients cannot control all factors that
increase the risk of heart attack, such as age or race,
pregnant women can take some steps to prevent an occurrence,
James said.

"Women should fully understand the potential dangers that
come from pregnancy at a higher age, and they should either
change their lifestyle to lower their blood pressure or control
it with medication," she said. "They should also quit smoking.
Also, pregnancy is not the time to lose weight, but achieving a
healthy weight prior to conception can lower the chances of
cardiac distress."

Two limitations could affect the study, James said. Because
the data came from a national database of hospital discharges,
detailed information about individual patient diagnoses was not
available. Also, 3 percent of patients transferred facilities,
so they could have been counted twice.

In addition to James, co-authors are all associated with
Duke University Medical Center and are Margaret G. Jamison,
Ph.D., Division of Epidemiology, Mimi S. Biswas, M.D., MHS,
Division of Cardiology, Leo R. Brancazio, M.D., Division of
Maternal and Fetal Medicine, Geeta K. Swamy, M.D., MHS,
Division of Maternal and Fetal Medicine, and Evan R. Myers,
M.D., MPH, Division of Epidemiology.

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